1) I'm typing this in a pixel 7 pro running grapheneos. I'd say these are plenty good enough. Device support is pretty solid compared to cyanogenmod of previous times. App installation is a bit slow using sandboxed play store. Not sure why that is.

For security reasons, GrapheneOS uses ahead-of-time compilation for apps. The stock OS compiles the heavily used parts of the code dynamically in-memory and then does partial ahead-of-time compilation later in the background. The install-time compilation will become more asynchronous in the future so the app can be used right away.