Definitely a trade off between energy and security. I have PBS running on an old laptop backed up to Backblaze and wouldn’t change it for anything, though. Proxmox backups are flawless and have saved me so many times. But yeah, 16GB of RAM with that processor is overkill for PBS and will probably consume more energy than is needed.

If everything is Dockerized anyway, you could just skip the step where you backup to PBS and use something like Kopia to backup your Docker volumes to a network share or offsite, rebuilding with compose or whatever if you have an issue.