If you run something like freenas i’d suggest setting up owncloud/nextcloud and working out of your synced folder for really important stuff.
If your NAS breaks, your important stuff will be synched to your workstation PC, and vice versa.
Combine that with ZFS snapshots on the owncloud/nextcloud dataset and you’re safe from synchronisation fuck up, if that was to happen, also.
Also, just on backup.
If you were to go for say, 3x hot-plug drives in a 3 way mirror, you could perhaps remove one periodically to use as an off-site backup. Plug it back in , let it re-silver and then remove either that one or a different one next week/month to keep off-site.
You’ll still have hardware redundancy with the 2 drive mirror that remains, and if you have a failure, just pop the backup drive in for a fast rebuild as it will already be mostly synchronised from before you popped it out. ZFS only rebuilds what is missing.
If you have total system failure (house burns down, etc.), you’ve got your 1 off-site drive with (most of) your data on it that you can import into anything that can run ZFS to get your stuff back.
No need to fuck about waiting for backups to happen, just pop a drive out. Mirrors are a wonderful thing . Sometimes, the best/most convenient backups are the ones that require no time or effort to do…
Alternatively, zfs send/encrypt your stuff to a cloud provider.