Happy Fairphone user here. Fairphone OS installed by default (pretty minimal without much bloatware).
Haven't tried it myself, but if you want to go further, they have guides for installing /e/OS or other OSes, they support that, and reverting to Fairphone OS if you wish.
No idea, sorry. The phone has NFC but whether your bank has an app you can get without the Google Play Store is dependent on your bank, but often not the case. If these are deal-breakers to you then it's going to hard to recommend all-in with /e/OS at the moment. You could also try it and revert to Fairphone OS, they do support that, but presumably it's a non-trivial and time-consuming thing.
You could try running /e/OS on Anbox to get a feel of it and what can and can't be done? That's probably the simplest way forward.
Haven't tried it myself, but if you want to go further, they have guides for installing /e/OS or other OSes, they support that, and reverting to Fairphone OS if you wish.
https://support.fairphone.com/hc/en-us/articles/440585818958...