Intensifying sensations during meditation after switching to an Ayuverdic lifestyle

First, good to hear that you have your health in check thanks to the medical care you mention. With their attention, we could likely rule out the medical aspect of your sensations. However, i can't tell from your description if they have been consulted about the tightness in the neck and head you describe.

Does eating vegetables increase the "sharpness" of meditation?

It's more likely that eating vegetables keeps you from being dull or drowsy, by staying away from food that requires a lot of energy to digest. In fact, the sixth buddhist precept has this particular purpose.

Should I quit drinking coffee/using cannabis?

According to buddhism, substances keeps us in an unbalanced way of life due to craving (tanha). If you manage to reduce your craving habits it will help you develop better karma for yourself, in turn helping calm and concentration in accordance with the fifth buddhist precept.

This goes primarily for cannabis, as it is altering your perception/concentration, but also to a lesser extent coffee, since caffeine can prevent you from developing samatha or tranquility during meditation.

I am intrigued by what is happening in my body and have no clue which person I should consult about these sort of things. I am a vata/pitta individual living in the Netherlands.

The experiences you have are addressed in many different traditions of thought. Buddhism very much provides a framework for understanding and dealing with your questions, but may/may not correspond to ayurvedic practice (i know practically nothing about those things).

Put shortly, what you are experiencing could be considered citta sankhara, or formations of perception as a result of your habits, generally speaking. Provided it's not a medical cause for your sensations, they will probably be stilled if you continue your meditation practice.

The Noble Eightfold Path is conditioned but can be grasped too tightly from a desire for rapid progress or attainments. Embrace slow, steady and gentle practices and observances. Observances and practices that lead to obsession are not skillful. Find a middle ground that leads to less craving, less aversion and less delusion. In the practice of Buddhism, we let go of our cravings. We don't grasp them.

Thag16.7:6.1: Today I am fortunate, persistent, happy with the scraps in my bowl: Bhaddiya son of Godhā practices absorption without grasping.

Regarding diet, when I wore a glucose monitor, what I noticed is that subtle changes in diet have great impact on glucose levels. Eating a banana alone causes a glucose spike. Eating a banana with peanut butter smooths out the spike. So it's not just what we eat, it's also how and when we eat. Be gentle with your body and observe it mindfully and carefully in consultation with good doctors and teachers.

Many people have described "spiritual" or energetic feelings after changing their diet, particularly vegetarian/fruitarian diets, without those people necessarily practising meditation or following a relgious practise. Buddhist monks have sometimes been encouraged to eat meat if their health was poor/they were sick, and the Shaolin monastery monks practising kung fu eat meat as part of their training, although their meditational practise may be limited. Although I have not personally noticed any changes in my Buddhist practise from reducing my meat/fish intake, it is possible that, as another user has said, that you are more focused because plant food digests more quickly. It may well have made you more sensitive, but I have no proof of that. However embrace these changes as something positive. As you diet becomes cleaner, you may react to those unclean parts of your diet: eg coffee/cannabis and quite naturally want to reduce them. This has happened to me with regard to my coffee intake. As my diet has cleaned up, coffee occasiaonlly tastes toxic to me, even though I generally love it from and have been addicted to it for a long time.