I found the instructions on the website to be completely adequate.
https://grapheneos.org/install/web
You’ll still be able to use Google Play and the apps found there, if you want to. I’d heard of people having trouble with banking apps. I access my bank using their website, not an app.
Just understand going into this that the priority is privacy, not compatibility. Maybe keep your old phone around in case there’s some must-have app that doesn’t work but you need occasionally.
I don’t have any complaints about the performance of graphene on my pixel 7a but I don’t do much outside of texting and browsing webpages. I also get about 3 days of battery life out of a charge.