Best option for adding storage

I bought the low-end system (110) and I need to add some type of USB 3 storage.

I'm not to well-informed on this: Would an external SSD or an M.2 (inside an external enclosure) be significantly faster than a 'regular' 7200 rpm external hard drive -- or will USB 3 somehow limit the transfer speeds on an SSD or M.2 to something less than their transfer rates when connected internally?