Payments don’t work, because of the play integrity api. But the bank apps that I use do work, even though they didn’t in my previous phone that was running a custom ROM with magisk to hide the tampering. GrapheneOs supplies their signatures so that app developers can support it, but I imagine not all will.
For me it has been a great experience so far. Installation was easy and fast, the privacy settings are great and almost everything works for me just fine. I had a couple of issues that was able to fix by searching for it on their forums, which is quite active
Nfc payments. Google pay doesn’t work. I believe any other doesn’t work either but Im not 100% sure. I never used them