Yeah, I’ve tried full system snapshots, and I find that it works better for me if I back up the data with plans to reinstall the OS separate from the restore.
I know that sync is not backup, but I consider my solution to be backup since all filesystems on the NAS are snapshotted, and snapshots are kept for hours/days/weeks/months.
I also try to automate system rebuilds – my macOS rebuild is pretty well scripted at this point, and some of my Linux systems have automated builds with Ansible. I would like to get more of that automated, but it will take a long time, and I’m straying far from the OP’s topic.