btrfs can pool disks just fine. Create a RAID nice and quick.

There’s also btrfs send and receive. Which may be what you need for shipping the data? You can use SSH for a secure write…

If this is a one-time copy, I’d strongly consider just syncing the data vs. shipping drives (which, as people have pointed out, may have serious reliabilty concerns).

Otherwise, if you must ship, I’d say the best move is two copies of each piece of data, so any single drive failing in shipping isn’t a big deal. But not a RAID. Just two literal copies on two separate drives. Simplest way to ensure some redundancy.