External drives · Space on the drive
Does a moved folder take the same amount of space on the external drive?
Short answer: Roughly the same. Sizes are measured as space used on disk, and space-efficient files such as some virtual-machine disks and disk images stay efficient on the fast drive. The drive's format can cause small differences.
Roughly, yes. Folder sizes in Storage Studio are measured as the room they take on disk, which is also the room you get back by moving them. Space-efficient files — some virtual-machine disks, disk images and pre-allocated databases that use less than their apparent size — keep that efficiency when moved to the fast drive instead of growing to their full size.
Small differences can come from the drive's format (APFS and exFAT store small files differently), and an APFS drive can show slightly different numbers to your Mac's drive.