NatWest and Monzo work fine on my Pixel 9a running GrapheneOS. Community maintained list of supported banking apps here:

https://privsec.dev/posts/android/banking-applications-compa...

Google Wallet is not supported at all.

Curve works and you can set that up as a replacement for Google Pay.

with avbroot ?

I didn't have to do any resigning or repacking apks. It just worked installed from the play store.