Hey, sorry nobody has replied to you. I've become very interested in the topic of the "best backup" solution for unRAID.
Duplicati on the surface seems pretty awesome. However, a lot of users including myself had nothing but errors. It still needs a lot of heavy development.
I wrote a guide on combining RCLONE+BORG. Borg does a really great job at creating your repos while utilzing compression, deduplication, encryption, pruning etc. And you would then use RCLONE to push that BORG repo up to your offsite storage. The guide is here https://www.reddit.com/r/unRAID/comments/9md2hh/tutorial_rclone_borg_for_your_awesome_backup_needs/
Lately though, I stumbled across Duplicacy. This piece of software is pretty awesome as it's faster than BORG in some benchmarks AND it uploads to the cloud or locally without the need of using RCLONE. @walle wrote a pretty cool guide here. https://forums.unraid.net/topic/73796-solved-install-duplicacy-install-binary/?tab=comments#comment-687737&searchlight=1
Let me know if you have any specific questions.