The studs were staggered (outside wall flush to outside corner, inside wall flush to inside corner), but it could be done either way because they're not touching. I set the double mudsills down, each wall section, and then a 2x10 cap plate. I avoided a single mudsill because of the crappyness of PT SYP.

If you want to do your light double wall system, then I'd turn the inside studs horizontal (especially on one of your germanic frames with loads of intermediate nailing surfaces). Also, I'm no engineer, but I don't think that it really matters (in this case) where the sheathing is. The enclosure is it's own structural system. But if you want to stick something relatively inexpensive in the middle, then you could use Thermoply or Dow SIS.