Dude you're in for a treat. I went the same path, grapheneos, looked around , tried calyx, didn't like the fact that my personal data is being scrapped up by the Germans, and decided to go back to google.
Bought a p6p, had a ton of issues with stock, tried grapheneos, installed the play store
services, and now I'm not looking back.
It's plug and play and I can poke holes willingly into the iron tight wall that is GOS whereas calyx is just lolwtfbbq tier.
Just open up the "apps" app and install all 3 Google files. Any comparability issues and the settings for each app fixes it.
Solid project and solid devs.