My nextcloud is not 1TB, as interestingly I don't really use if for files but far more so for the nextcloud apps and as a sync server for various other things.

The 14 copies probably are not needed. I do this because I have space for it (I think nextcloud backups are about 2GB each for me). In your case aiming for three is probably fine, certainly better than two. I'd likely only keep the three copies if mine were that large. You could also investigate backup options that only backup changes and not every file every day.

My main concern is if I accidentally deleted a bunch of files, then that deletion got synced to the other copies. That's why I zip up daily copies and keep them for a couple of weeks, just extra protection. Finding a good incremental backup tool (that let you roll back changes) would probably provide the same protection anyway, I haven't looked into this myself though.