bushraptor Using GrapheneOS with Sandboxed Google Play doesn't defeat the purpose of GrapheneOS at all. The entire concept behind it is that with Sandboxed Google Play, those apps are bound by the same exact restrictions that all other apps you install on your device are restricted by.
One thing I notice is that people who decide to use GrapheneOS also simultaneously decide to completely switch up their workflow/habits all at once. They then get overwhelmed and give up.
If you're just moving to GrapheneOS and can restore you game data by using Play Store, I say go ahead.
Install GrapheneOS, install Sandboxed Google Play by following the official documentation and forget multiple user profiles and all other kinds of novel setups for now.
Take things slow :) I hope that helps.