When it comes to commercial products, is there harm to choosing a more beautiful and well-designed option?

As a householder one uses money and it is said in the vinaya that sensuality is then allowable.

It also forbids monks

Not to affirm that things such as sexual pleasures are not an obstacle to the development of ariyā stage or to jhāna realisations, nor to rebirth in the deva world, when the Buddha explains that these things are precisely an obstacle to those, and not to maintain erroneous views.

I don't liken buying a kettle to sexual intercourse but if it is something one experiences a desire for due to it being pleasing then it is on a spectrum where one gives attention to the theme of beautiful in regards to form & sensuality.

Householders are generally taught to sometimes uphold extraordinary discipline & perdiodically seclude themselves from unwholesome states.

Eventually they will incline to seclusion, will want to train not permitting sensuality and abandoning it altogether.

In as far as sensuality goes one should guard the senses but also stay comfortable. Therefore moderation is good and if one is inclined to seeing danger in small transgressions then one will want to be a monk quickly.

I am recently joined and my response as follows. Buddhism is self realization of the truth of Life. Meaning of Buddha is Truth and Dhamma is existence or life. Buddha Dhamma is Truth of Life. Buddhism is mechanism to the Truth. Once you are in the right path what you experience in the material world does not make an impact in day to day life.

You need to select best for you to continue this Life with required standard. This standard is varying from person to person. So if it is your preference to select best available as per per your norms, there is nothing wrong in that practice according to Buddha teaching. Good luck

I don't know your background but I think it is a big misunderstanding many people brought up in western worldview (like me) have, that you are not allowed to X.

I think an important part here is the Middle Way. It is perfectly fine to choose the kettle you like as long as you see a difference. Buddhist practice will ultimately lead to not seeing a difference (in value) anymore.

Just imagine a friend has two candies of the same kind. They are equally big. He holds both hands in front of you one candy in each hand and you are to choose one. You will most likely just take any one of them. How did you choose? You really felt they are the same thing, didn't you?

Why are there rules for Monks then?

This is a summary probably someone with better knowledge of the scriptures will have a more accurate explaination. Suppose you are trying to learn an art or a craft. You start as apprentice of a master in the field and just mimic whatever your master does. Do you know why you are doing it this way? In the beginning probably not. But with time you will see how doing it the same way your master does it leads to the desired outcome. "Ah now I see that X will lead to Y"

Counterintuitive living the homeless life is a luxury. Although it is open to anybody only people that have/feel no responsibility to certain people or things in this life feel free to choose it.

At a minimum, lay followers are meant to undertake the training of the five precepts, and observe Right Livelihood for lay persons.

However, if they decide to observe the practice of Uposatha (usually at full moon and new moon days), which is optional for lay persons, then they must observe the eight precepts which includes temporary abstention from luxuries for the period of Uposatha.

The five precepts:

1. I undertake the precept to refrain from destroying living creatures.
2. I undertake the precept to refrain from taking that which is not given.
3. I undertake the precept to refrain from sexual misconduct.
4. I undertake the precept to refrain from false speech.
5. I undertake the precept to refrain from intoxicating drinks and drugs which lead to carelessness.

"Monks, a lay follower should not engage in five types of business. Which five? Business in weapons, business in human beings, business in meat, business in intoxicants, and business in poison.
AN 5.177

There's nothing wrong in a lay person enjoying his own wealth including buying and using a "nice kettle". This includes spending for own self, one's family members and friends.

He is however recommended to contribute to charity. Please see this answer to understand altruism and charity in Buddhism.

In the following sutta quotes, the Buddha says for a lay person:

• one quarter of one's income should be enjoyed
• don't be a spend thrift and don't be a penny pincher
• be debtless
• save one quarter of one's income for future misfortunes
• invest two parts of one's income
• be charitable

Of course, for a person seeking full enlightenment, becoming a monk and forgoing luxuries become mandatory. That's a different story.

The wise endowed with virtue
Shine forth like a burning fire,
Gathering wealth as bees do honey
And heaping it up like an ant hill.
Once wealth is accumulated,
Family and household life may follow.

By dividing wealth into four parts,
True friendships are bound;
One part should be enjoyed;
Two parts invested in business;
And the fourth set aside
Against future misfortunes."
DN 31

"And what does it mean to maintain one's livelihood in tune? There is the case where a lay person, knowing the income and outflow of his wealth, maintains a livelihood in tune, neither a spendthrift nor a penny-pincher, [thinking], 'Thus will my income exceed my outflow, and my outflow will not exceed my income.'
AN 8.54

Knowing the bliss of debtlessness,
& recollecting the bliss of having,
enjoying the bliss of wealth,
the mortal then sees clearly with discernment.
Seeing clearly — the wise one —
he knows both sides:
that these are not worth one sixteenth-sixteenth
of the bliss of blamelessness.
AN 4.62

This was said by the Blessed One, said by the Arahant, so I have heard: "If beings knew, as I know, the results of giving & sharing, they would not eat without having given, nor would the stain of selfishness overcome their minds. Even if it were their last bite, their last mouthful, they would not eat without having shared, if there were someone to receive their gift. But because beings do not know, as I know, the results of giving & sharing, they eat without having given. The stain of selfishness overcomes their minds."
Iti 26

"The Great Way is not difficult for those who have no preferences.

When love and hate are both absent, everything becomes clear and undisguised.

Make the smallest distinction, however, and heaven and earth are set infinitely apart.

If you wish to see the truth, then hold no opinions for, or against, anything.

To set up what you like against what you dislike is the disease of the mind.

When the deep meaning of things is not understood, the mind's essential peace is disturbed to no avail."

-The Hsinhsinming (verses on Faith In Mind), attributed to Third Chinese Zen Patriarch Jianzhi Sengcan

We can take this as characteristic of the strongest kind of challenge to our moving through life by choosing what we like or dislike, by using desire and aversion. It is fundamental to Buddhist practice, to go beyond such a way of engaging with the world.

Does that mean choosing what we don't like to 'spite ourselves'? That is as problematic as choosing what we like. The task is to go beyond this, and the effect of desire & aversion on the mind.

I can't help but think of a non-Buddhist poem, by Rilke, which I think puts a very good response:

"So many live on and want nothing, and are raised to the rank of prince by the slippery ease of their light judgments.

But what you love to see are faces that do work and feel thirst.

You love most of all those who need you as they need a crowbar or a hoe."

-from The Book Of Hours

Aesthetics of a kettle are part of it's use. In a tea ceremony, widely given in China as tribute for patrons of monasteries, tea ware is very carefully selected. In Japan tea ceremony is entirely associated with Zen, and aims to make manifest the three marks of existence: impermanence, no unchanging identities, and intrinsic-unsatisfactoriness. This is through ideas like wabi-sabi ('rustic beauty'), ichi-go ichi-e ('this meeting is for one time only') and kin-kei-sei-jaku (humble reverence; a respect for the food and drink; purity of both body and spirit; and calmness regarding desire).

So with something as simple as sharing a cup of tea, we can practice the whole of Buddhism. Ikkyu Sojun said "the Buddha dharma is also in the Way of Tea", and his student Murata Juko is said to have realised awakening through it.

It's not that each cup of tea has to be an earth-shaking revelation. Zen Master Dogen wrote about the relation of ordinary activity and awakening in his fascicle Tea and Rice. He even taught his monks how to go to the toilet mindfully, so it is not about the elevation of tea. Buddhism is non-dualist, there is not an ordinary world and an enlightenment world, they are the same. It is about awakening to what was there all along.

Nice tea kettles are indeed beautiful. Yet beauty and love alone do not quite span the scope of the heart.

SN46.54:12.9: The apex of the heart’s release by love is the beautiful, I say, for a mendicant who has not penetrated to a higher freedom.

Focusing only on the beautiful bypasses the ugly. There will always be ugly tea kettles. And what shall we do when our beautiful tea kettle gets banged up, scratched and tarnished? What shall we do if we see a more beautiful tea kettle? So much diversity of form! Augggh!

Although beauty is indeed the third liberation...

DN15:35.7: They’re focused only on beauty.
DN15:35.8: This is the third liberation.

...it is followed by the fourth liberation:

DN15:35.9: Going totally beyond perceptions of form, with the ending of perceptions of impingement, not focusing on perceptions of diversity, aware that ‘space is infinite’, they enter and remain in the dimension of infinite space.
DN15:35.10: This is the fourth liberation.

What is this fourth liberation? What is this "space is infinite?"

It is the heart's release by compassion. Instead of turning away from ugliness, we integrate that perception of ugliness into our perception of beauty. And within this infinitely spacious embrace we find peace and harmony with all manner of tea kettles. We brew and welcome tea no matter what tea kettle makes it.

SN46.54:13.7: The apex of the heart’s release by compassion is the dimension of infinite space, I say, for a mendicant who has not penetrated to a higher freedom.

There are four more liberations. Welcome to Buddhism!

OP: "This might sound ridiculous as a jumping off point but it made me consider my attraction to certain products rather than others."

Actually, it is a remarkably astute jumping off point.

OP: "I really want a kettle that is well designed aesthetically and that has more advanced functions like temperature control, but it feels like this is a form of grasping of sensory pleasure."

There is nothing intrinsically wrong with wanting to have a "nice kettle" that fulfills its function and is also beautiful to you. The problem arises if you believe there is any such thing as an objectively existing "nice kettle." If you look carefully at your mind as it perceives and conceptualizes this "nice kettle" you'll find that it is an illusion based upon your own predilections and habits. That "nice kettle" says more about your mind and karma than any actually existing "nice kettle" out in the world.

It is like the story of the God, the Human and the Hungry ghost all arguing over a cup of liquid. The God tastes it and declares that it is the nectar of the gods. The Human tastes it and observes that is just clean water. The Hungry ghost tastes it and perceives blood and pus. None of them is objectively right, but each of them is subjectively right. There is nothing about that cup of liquid that makes it ambrosia, or water, or blood and pus.

The same is true for your "nice kettle." So, observe your mind and how it is conjuring the "nice" and superimposing this. If you do and penetrate deeply the illusion will start to lose its enchantment letting you just buy your "nice kettle" without getting wrapped up in craving for it.