[tnbp]

1. Doesn't matter. ZFS or whatever. I use ext4, it's good enough.

2. Buy as many 3.5 inch external USB drives as you need to reach 23 TiB, then connect them all over a single USB hub. Buy the same drives again, shuck them, and stuff them in this[1]. Store them in one of these[2] when you're not doing a backup and put it somewhere outside your home. Merge them all using mergerfs.

3. rsync. If you need to think about how precious your data is, at 23 TiB, you've already lost. Just backup everything in triplicate. Don't bother setting up RAID; it's not a backup.

[1] https://www.amazon.com/-/en/dp/B07MQCDVJ2/ [2] https://www.amazon.com/-/en/dp/B087WXFFW6/