I don't know how to answer to this, other than you seemingly don't know Android so much.
Everything you describe here is normal on all Android (e.g. differences of UI or differences of default apps). F-Droid has nothing to do with GrapheneOS.
> Exploit protection compat mode for banking apps.
This is the only caveat: some (not all) banking apps are annoying.
The UI is not the same nor are the app defaults. Combined they create a different UX from stock Android.
The default graphene App Store, and expected apps found there are different than Google Play or what you'd find on Google Play.
The default permissions of each app are restrictive, most notable when you start mixing App Stores.
F-Droid culture, and the app options, are their own thing.
Vanadium, the graphene messaging app, the lack of forced updates and nag buttons.
Exploit protection compat mode for banking apps.
Motorola isn't selling to you or the other person that responded. For that market graphene will have an unexpected learning curve.