For time being you're limited to Pixels. Some Motorola models in a year or two. Installation is a breeze. You can run completely Google-free or install Google Play services in a sandbox, so you could install them in a common shared or separate profile.

https://grapheneos.org/faq

GrapheneOS only support Pixel devices.

Can you run common apps from the play store if you choose?

https://discuss.grapheneos.org/d/10855-google-play-store-install

I think you can install Google Services (including Play Store) if you want, but there are alternative like Aurora Store that lets you download apps from Play Store without Google Services, but obviously you can't buy apps from it

the main concern is probably banking apps or some apps that require Google Play Services to run

Currently, graphene can only be installed on Pixel phones, but Motorola will be releasing phones that are compatible although I'm not sure when. Graphene runs a "sandboxed" version of the play store. You can get just about any Android app and your apps can't really talk to one another or to the play store. Occasionally you'll find an app that doesn't work. If you want more detail you can join the graphene OS discord. It's pretty quick & easy to install.