Btrfs doesn't have encryption, so you need to do it with luks to an mdadm raid, and build btrfs on top of that. Luks on mdadm raid is known to be slow, and in general not a great idea.
Why involve mdadm? You can use one btrfs filesystem on a pair of luks volumes with btrfs's "raid1" (or dup) profile. Both volumes can decrypt with the same key.
I feel like that purpose has already been undermined by various changes to copyright law since its inception, such as DMCA and lengthening copyright term from 14 years to 95. Freedom to remix existing works is an important part of creative expression which current law stifles for any original work that releases in one person's lifespan. (Even Disney knew this: the animated Pinocchio movie wouldn't exist if copyright could last more than 56 years then)
Either way, giving bots the 'right' to remix things that were just made less than a year ago while depriving humans the right to release anything too similar to a 94 year old work seems ridiculous on both ends.