All my banking apps and credit card apps have worked flawlessly on Graphene OS. You're correct that tap to pay doesn't work, which is a bummer. But that is just Google spyware as well, honestly.

I heard about this a while ago, but I remember the GrapheneOS team talking about suing Google if they didn't allow them to pass play integrity checks like they should be able to, but Google just doesn't let them. That's the only reason tap to pay doesn't work and some baking apps have issues, its Google purposefully limiting graphene OS so they have a competitive edge somewhere.

Plenty of bank apps work just fine. None of the ones I've tried had problems, except Santander, which works perfectly after changing a setting.

Personally I don't need or want any of those things on my phone.

No they work. It's not like LineageOS. Both Bank apps I now need, work on GrapheneOS but did not on LineageOS. It is my compromise without being compromised.

You can do online banking via a browser, it's clunky but you generally just need to be more prepared

Manageable.