Is there anything wrong with this money/security plan to travel to "just about any country"?

Regarding currency, my usual go-to plan is to take local cash with me, usually as much as I think I will need for the trip. I keep my cash in my suitcase usually, and only carry on-person enough money to tide me over for as long as I'll be away from my hotel (essentially, my hotel is my ATM).

Cards often charge fees for conversion/withdrawal/transactions overseas and that's not something I find value in, and dealing in local currency is much easier than trying to deal with other currencies; many countries do not (commonly) accept even the USD at local businesses, because dealing with foreign exchange is a pain in the ass for small business owners. So I'll usually bring most of my budget in local currency.

That said, this strategy only works if you are comfortable that your luggage won't be stolen. I take that as a "cost of doing business", so to speak, of traveling: If I'm staying in a hotel, I'm assuming the hotel staff isn't going to steal my stuff, and that's just that. Of course, my suitcase with my money in it is locked unless I am physically looking through it (I lock and unlock it each time I open it), and my hotel door is locked unless I'm inside or the hotel staff are cleaning it, so nobody has access, and if I'm in transit, my luggage is always within arms reach unless I'm on a mode of transportation which doesn't allow that, and in that case I'll put my money on my person in advance in case my luggage gets stolen. I don't stay in group lodgings with strangers as a general rule, it's just not something I do.

The bottom line is, plastic tends to cause problems, and foreign exchange tends to cause problems. It's easiest, when traveling, to use local currency cash as much as you can, rather than trying to rely on everyone accepting a USD credit/debit card.

About bank cards:

Pack my VISA debit card

That is a big security hole. A thief might have access to all your money – take a credit card.

Who the hell has two bank cards?

I have two credit cards. I use one for online purchases and one for in-person purchases. If one gets compromised, I can still spend by using the other. Neither has any fees (unless I can't pay them off) except for cash withdrawals, and the number of cards you have does not affect that.

About cash:

You'll usually need a small amount of cash, if only to tip. But remember that the local people may have a very different idea of what "a small amount" means. Bear in mind that in some parts of the world, people might earn one dollar a day, or less.

I would add another precaution:

6. Take a reasonably large (but not so large it cannot be used) denomination bill in a currency that can be exchanged or accepted practically anywhere, for example USD. Hide it away from the other important stuff.

What does "enough money on my bank account" really mean - enough money for what? Enough money for everything you plan to spend - of course But also enough money for potentially foreseeable problems such as having to change your flight ticket home, spend an extra couple of nights at your hotel/accommodation, purchase travel back to the airport from wherever you are etc.

Consider Travel Insurance. Basically this falls into two categories although they can be combined in the same policy. First, insurance regarding the actual travel - repayment of sunk costs if you have to cancel the whole trip, or compensatory payments for being delayed or your baggage lost. Second, medical insurance to cover everything from just having to visit the doctor/dentist for something minor but painful enough to ruin your holiday to full on accidents, hospitalization and at worse, medical evacuation back to your home country. For many people the cost of the travel insurance is an extra burden for something they won't need but if you don't have it you do want to at least consider how you will access & pay for healthcare while abroad.

In these days of easy internet access you expect to always be able to look up information you need, but for security, I would also suggest having an old-fashioned piece of paper with the most important phone numbers on it, such as how to call your bank from abroad (not always the same number as you would normally call), the lost/stolen phone numbers for your credit card, your travel agent if you use one, the access number for your airline, a number for your phone provider and even the Embassy or Consulate in the visited country. All of these should already be programmed into your phone of course, but having them on paper in the hotel is a backup in case your phone is lost or stolen.

It is a fair reasonable plan but it is also hard to generalize this to all countries. Let's see how we can improve it:

• Make sure you have or will have enough money for planned expenses, any automatic spending at home (such as automated bill payments and subscriptions) plus an extra buffer for travel. There are frequently extra unexpected costs while traveling. Budget about 20% extra if you have Travel Medical insurance, otherwise increase your reserves further.
• Informing a bank is no longer essential and some will outright say you no longer need to do this. If you can tell them, go ahead, it could help when something triggers a fraud warning.
• Pack one bank card and ideally one credit card in your wallet with an ID. Generally, I use my local driver's license since it is less valuable to thieves but looks official enough to be trusted.
• In addition, always have a copy of your passport. In countries where you are not required by law to carry your passport, keep it in the hotel safe and take the copy with you. Elsewhere, carry the passport when legally required and keep the copy in the hotel. This will give you something to show in case your passport gets robbed. Myself, I also leave a second official ID in the hotel.
• Taking out local currency when landing is a good idea. The amount will depend how much cash-oriented the local economy is. Some place can be managed entirely with cards but there are places where cash is often used for certain types of spending such as street-food, snacks, outdoor markets and tipping.

It is very important that you have two types of bank cards. Not just from different banks but more importantly from different networks. Most VISA/Mastreo Debit and VISA/Mastercard Credit Cards are indeed accepted very widely but not everywhere. So by having one of each, you can improve your chances of having a card that will be accepted locally. UnionPay is another one that covers many areas where others are not accepted. It may be overly cautious but I usually carry two with me and two in the hotel safe, one of each kind in different places.

Over my travels, the most common issue I faced is a card being unsupported. In Indonesia, only HSBC worked and the same in Iceland at gaz stations (although other cards worked in other places in Iceland). Brazil really had trouble with my cards issued from Canadian banks, not because these card were unsupported but because the transactions were frequently rejected due to security alerts.

You mentioned a debit card but credit cards are more useful and I highly recommend you travel with one. This will let you pay for unexpected costs but also credit cards have a mechanism for merchants to place a hold on a certain amount. This is nearly always required when renting a vehicle but there are plenty of other cases when certain activities require a deposit.

For "just about any country", this is definitely not enough.

First, in some countries, cash usage may still be prevalent, and ATMs few and far between. For those countries, you'll have to take quite some cash.

Next, if any issue arises, a credit card is probably a much better option than a debit card (you usually have a lot more protection). Also, insurance is a must, so either book your whole trip with a card that includes decent insurance (credit cards are more likely to include that than debit cards, but this varies a lot), or buy insurance in addition to your trip. Make sure you check exclusions, especially these days (many policies will exclude travel to any country for which an advisory has been issued, which is most of the world these days).

Having more than one card is strongly advised. Even if you tell your bank that you are in country X, sometimes things may be blocked without you knowing how or why or by whom. Having a different card from a different issuer, ideally on a different network is always a good idea. Don't know where you are, but in many countries it's possible to get a new account with a card easily, either for free or with very low fees. Shop around.

Of course things are very different if you're a German travelling to France or a US citizen travelling to Afghanistan. I'm not sure there's a one-size-fits-all solution.

This is way more than I have ever done over the dozens of countries I’ve visited in all parts of the world, from places like USA to Zimbabwe to Brazil to China, and for trips ranging from backpacking in hostels to 5* hotel leisure trips to 18 hour work days at a remote office.

1. No one has ever asked me for proof of my bank account situation on arrival. I’d probably assume the official was corrupt if that came up outside of applying for a visa in advance.
2. Banks in the UK stopped caring about foreign travel as soon as chip-and-pin came in. I think I’ve had a card blocked twice while abroad, which is less than at home. In both cases it was resolved with a quick phone call, and I used a different card in the interim. Maybe things are different where you are — but are you sure or are you speculating?
3. I just pick up my wallet and walk out the door, same as if I’m going to the shops. I don’t have a separate RF-proof travel wallet. It sounds like something extra to remember when I’m late for a flight.
4. Ok, you win this one: I usually leave my passport in the hotel, unless the destination country explicitly requires me to carry it. That’s mostly out of laziness than security.
5. I rarely bother to obtain hard currency unless I know I will need it for certain: the unused cash ends up in an envelope of foreign currencies I never spend and forget to take next time.

If it is easy and free in your country to get additional cards, do so. Look out for cards with zero FX loading (not just “no FX fees”). Obviously you don’t want to pay a fee for something you won’t use, but debit cards are often expensive to use outside of your own country. The added security of an extra card is worth far more practical value than the rest of your (slightly paranoid IMO) list.