Double-X movie film is interesting, but it's not Super-XX. Double-X comes in cine formats (maybe just 35mm today, possibly 70mm) and produces a grainy image with relatively low contrast designed to be copied to print film. The film has a lot of latitude and is interesting to experiment with for still photography if you like the gritty look. It does well in high-energy developers like Dektol and Acufine.

Super-XX came in sheet sizes (maybe at some point it came in rollfilm formats) and was known for its long scale and straight-line curve. A have some in the freezer that I'm hanging on to for the right project.