How do you back up and restore things without root? I've found that even with root, these days many backups are useless thanks to using hardware-backed encryption...
(not OP but been on Grapheneos for a couple of years).
I don't. I transfer any important data like photos to a real computer weekly
Mail, Calendar and Contacts are handled by IMAP and DavX. Passwords are in 1Password
I have minimal apps so setting up a new device wouldn't be too much trouble
There are various options, but if you use syncthing, it is as easy as creating a share on your PC or backup machine and on the phone. Everything gets synced automatically.