Yeah, I meant the Windows Storage Spaces drive pool.
I currently have 3x 20 TB and 1x 18 TB allocated to the drive pool as storage space and only using 32 TB at the moment. I don't have any spare drives of capacity to move files between; the remaining drives are NVMe drives ranging between 1 and 4 TB with one of them as the system drive. Due to the space I have, I could remove one drive at a time to recreate the pool in Stablebit and transfer files overnight. Plex is rather fussy about the drive letters if I don't go in manually into the registry to change the location. But if I do the move overnight (or, well, 24 hours) on a day I don't need it, that wouldn't be a huge hit.
Backblaze hasn't changed on restoration process if a drive fails.