It depends a bit on the filesystem that you are choosing for proxmox however. Afaik there are still problems with zfs as the host filesystem and docker in an lxc. the general recommendation is to use an extra virtual disk that is ext4 formatted for /var/lib/docker.

I do remember my joy, when finding out that instead of feeding it with batteries, I could even use the power adapter of the master system to play with the Gamegear. 😄

Another +1 for restic. To simplify the backup I am however using https://autorestic.vercel.app/, which is triggered from systemd timers for automated backups.