I use a Raspberry Pi too and my backup solution is almost the same as you and for me it have worked for restoring. I must say, thanks to restic I restored a damaged raspi installation (I was the one who damaged the thing playing around with configurations). So, I make 1 4am snapshot every day and that’s it. I use --exclude instead of --one-file-system and these are my exclusions:
/root/*/.cache
/home/*/.cache
/proc/*
/sys/*
/dev/*
/run/*
/mnt/*
/media/*
/etc/mtab
/var/cache/apt/archives/*.deb
lost+found/*
/tmp/*
/var/tmp/*
/var/backups/*
As I have already said, it worked for me. I try to have most of my configurations in my user’s home because that way, if I need to restore to a new installation I mostly just need to restore my home files but there are always files needed in /etc, for example. My installation is pretty simple, I must say; I just use samba ssh plexmediaserver and I have a couple of custom startups services, cron jobs to manage backups and attached HDD’s that are encrypted. So, when I huged up my installation in the past, I just took my SD and restored damaged directories with restic and that was enough to make my raspi run again. That was about 3 months ago and it is still working like charm.