tuxcoders If i install google voice on my phone and login to my google account, I guess it will automatically log in to the containerized play store too
Yes. When you log in to a Google app, the account will be saved in Settings > Passwords & accounts, then other Google apps will use that login token to automatically log in.
tuxcoders Does google get to see data around what apps are installed
Any app can list installed apps. Whatever app you use for Google Voice could list installed apps too if it chose to.
I'm not sure what you mean by "data around". If the apps aren't Google apps, they have no access to any of the other apps' data. No proprietary Google app has privileged access to anything on GrapheneOS.
tuxcoders associated push notifications and link them to me?
As far as I know there's nothing stopping them from doing this. From what I can tell, push notifications are pushed to a "device ID", but I don't see why Google can't just associate a "device ID" with an account. (BTW, the device ID isn't a real hardware ID. I don't know where they get the ID, but I'm guessing it's a randomly generated ID just for push notifications.)
If you want to avoid Google tying you to your Google Voice account, you can always use a separate profile with a VPN for Google Voice