I have three identical Unraid servers. Each uses syncthing to synchronize all data so that all three are identical. I use appdata backup to keep all the docker containers backed up and, of course, those backups are synchronized to the other servers.
I've seen some requests here to change the single backup file into multiple backup files, one for each container. I like this not only because it makes sense and would be easier to identify the backup and its app but syncthing doesn't handle large files nicely. The bigger the file, the longer it takes.
https://forum.syncthing.net/t/poor-performance-on-big-file/8934/4