I use the tool I wrote. Using 10Gb networking I’ve found my sweet spot to be 7 simultaneous moves, but my plotter can’t keep up, I usually end up with 2 or 3 moves at the same same unless there is a backlog to clear.
use something like Plow to move files from your 1TB to the final hard drives.
It can be set up to move to one target at a time - I think that’s the default even.