Per that same shmups forum, user Jademalo was kind enough to get an answer for Xbox:
* Same PAR as GC (10:11)
* Same samplerate as GC (858)
* Different from GC, Xbox uses the full 720 pixels for horizontal resolution
As a result, 480p content should be resized to 654.55 (round up to 655) pixels wide.
I’ve updated my Google doc to match.