>>11944996
Bison II is a different version of Bison with more powerful attacks and different moves.
True Bison has infinite super gauge, is in permanent Excel Mode, can cancel every attack into itself (can do the same supercombo twice in a row) and his Meteor Combo is different.
The issue the anon above probably had is that the naming convention makes no sense. Bison II was a version of Bison in SFEX2 that was white and red:
https://www.youtube.com/watch?v=nBZcjsoZmW8
While Bison II in SFEX3 is just a stronger version of the normal final boss, and True Bison is SFEX2's Bison II. I think the confusion is mainly because of the color scheme, although the naming convention makes no sense.
About the paths in Original Mode, the issue I found is that the mid-bosses only appear if you're using specific characters, and not just anyone like in EX and EX2. To fight Kairi, you can only use Nanase or Hokuto (his sisters). To fight Evil Ryu you must use Ken, Sakura, Sagat or Bison.