Let's say you have here a public address and receive coins. Then you pay to someone, they are able to search this address and now they know it was you~ This is why I have never been confident using BTC for payments
Use different wallets for different purposes. If the address is publicly known, keep it away from your main stash. If you buy a coffee, don't pay with a 1000
BTC input. If you buy a jet, you can use the large input.
I would like to buy some services like an VPN, airBNB, cloud storage and more, that would be cool to pay with BTC, but spending it with any level of reasonable privacy and safety is a ton of work.
You could convert a small part of your coins to a privacy coin, and pay with that. AirBNB comes very close to real life, I wouldn't mix that with crypto. But for servers it's fine.
Food for thought: if you don't trust your VPN provider with your data, you shouldn't use them in the first place.
Back then you just used one wallet.dat. I don't see why you would different wallets when you can just create different addresses. The problem is, if you simply move 0.1 BTC from an address with 1000 BTC in order to have this 0.1 BTC to spend from, while for a simple p2p transaction this would at least give you an additional layer of protection since technically you are not seen as an owner of 1000 BTC anymore but 0.1 BTC, it is still a problem if:
1) You run out of this 0.1 BTC and need more BTC, which you would send from the 1000 BTC address into a new address. If you were to pay this same person or service, they would see it's a bit strange this 1000 BTC address is the same one again previous to your address. It proves nothing but it would indeed be not ideal.
2) The main problem: Once they deposit your coins in an exchange, the chain analytics software can go several steps before your transaction, so if the person or service knows who you are, they would point to you as the most immediate step to these coins.
If you are limited to anonymous online payments, then the use cases are extremely limited, and it would be for digital stuff, like an VPN subscription, or perhaps cloud storage, and I cannot even find a decent cloud storage service that accepts BTC without doxing.
I just would like to be able to pay for stuff, without this constant paranoid feel of not knowing if you are paying with "tainted coins", which is a thing no matter how much some want to deny this, because once again, if you or someone else deposits coins in a service using these "automatic audit" analysis tools, you can end up in trouble even tho you did nothing wrong, and good luck with that.