For me, the best part of Below Zero by far was seeing it grow and change over its development cycle. One day I would discover a new feature and then a week later it would be much more polished, and another two weeks later it would have moved to a different place and be revised again.
That was a once in a lifetime experience, too, and to me it was much more fun than the finished game. I'm glad I did it this way, and I hope it will be a similar experience with Subnautica 2. But of course I can see that there's a good chance it will just be an unfinished game with lots of spoilers.
I've found that the easiest and most effective way to backup is with an rsync cron job. It's super easy to setup (I had no prior experience with either rsync or cron and it took me 10 minutes) and to configure. The only drawback is that it doesn't create differential backups, but the full task takes less than a minute every day so I don't consider that a problem. But do note that I only backup my home folder, not the full system.
For reference, this is the full line I use: sync -rau --delete --exclude-from='/home//.rsync-exclude' /home/ /mnt/Data/Safety/rsync-myhome
".rsync-exclude" is a file that lists all files and directories I don't want to backup, such as temp or cache folders.
(Edit: two stupid errors.)