How do you backup your home lab?

Hey Guys, So i got 3 mini pc, 2 which i wanna use for stuff and the last as its also only got a pentium (2ghz 8gb ram), So i heared about borg and many many many other solutions. So im completely lost. I want to keep the backup on the 3rd minipc than on some remote system (maybe hetzner 1tb for 4€ not sure if there is something better/cheaper (tb/€ wise) Iam and will be the only user for the entire selfhosted services so i though at some point idk 03:00 or somthing everythin goes down backups are made, containers restartet or something? Or can i do this while containers are running?