I use RSnapshot and make incremental backups to an external harddrive, and (I know it’s not a backup) run my two RAIDs (one for media, one for general data) in mirrored mode.
When I eventually upgrade my home server, I will upgrade from 2x2 2TB drives in RAID1 to four 8TB drives in either RAID5 or 6 - I am still undecided if I am willing to sacrifice 4TB of capacity to the redundancy gods and get an extra harddrive that can fail without data loss in return.
Not in terms of the recommendations, but if you want a client for Subsonic or Jellyfin that is close to the Spotify UI, then I can recommend Sonixd.