Slurp
Although the links in the previous posts will answer your questions, I think it's enlightening to see just how much data Google doesn't get when you compare GrapheneOS with the Stock OS.
If you've used the Stock OS recently and logged in to your Google account, then did the same with GrapheneOS, try requesting a copy of your data from Google and compare what info they have/had about your phone while running both OSes. It's crazy different. Google gets virtually nothing when you're running GrapheneOS.