The only time I’ve willingly used a banking app is when they lock out my VPN IP. In those cases the app still usually works for whatever reason. So far, I haven’t found any functionality missing from the webapp, but I’m also dealing with brick and mortar institutions.
I would be concerned as they will eventually probably move to a phone app first ecosystem, however it will probably take a while. Some people are still only using in person and phone banking (where you call them and punch in numbers).
I believe cocks.li is still open, so you could use them. You said in another reply that you’re not savvy enough for your own domain, but if you change your mind, purelymail.com With your own domain, you can easily switch providers without losing access to your addresses.
I don’t feel there is any harm in having several accounts spread out for whatever purposes. Compartmentalize it so that each user is distinct and keep the accounts. I think this is the best way to maintain privacy but also not create new accounts constantly. Pretty sure this is good enough to not expose yourself.
I don’t know how safe this is, but what I do:
Spend it where you can, not many places. BTCPay server, which can be self-hosted, supports it, so there are options.