I've been using grapheneos on a pixel5a too, I've been trying to make the experience as minimalistic and distraction free as i can, here's some tips I can give.

First I disabled _all_ notifications, except for calls and sms. This choice makes things very calm.
I didn't install the play services neither, to see if it's usable.

About the apps, I have no play store, so I get all I can from f-droid.
I found two very simple launchers, one is "UnLauncher" which has no icons and no wallpaper, and "PieLauncher" which is very fast to use once you get used.
Signal and Whatsapp are not on f-droid, but you can download the apk from their website and they seem to work flawlessy.
Then, Antennapod is a good podcatcher (you can add the HPR feed too ;) ).
Lastly, I suggest using NewPipe as a replacement for Youtube; note that the f-droid build of newpipe is a bit old, but you can add their external f-droid repository to have faster updates.