Would the tracker blocking available on iOS at the OS level mostly suffice for this?
Not the person you asked, but no. Because that would mean you have to trust iOS to not track you. I can be convinced that Apple is less bad than Google in that regard, but if Apple has nothing to hide, then they can let me have root, so I can verify, right :) ?
Is this your custom ROM, or is it a widely known one?
LineageOS with MicroG
SafetyNet?
Are you somewhere where banks won’t let you use their website and force app usage?
NFC payments?
That’s fair. Although I personally don’t need that tied to my phone. Maybe it could be substituted with contactless cards?
The advantage of phone NFC payments is that there's no limit, unlike with a card which is usually capped rather low (50/100€ here in France).
Essentially but not exactly. Their website is unusable on a phone. Just switching from mobile mode to desktop mode after login will expire your session.