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.