There have been members posting here, that with equal gaps between the swing arm and frame, they get a slight 'ticking' sound from the universal joint when the rear wheel is rotated, most likely the universal joint is just barely contacting the swing arm housing .
Adjustments are made to the pivot bolts to silence the ticking, and the gap on each side of the swing arm ends up not being the same on each side .
From your description, I don't think I would be concerned about the offset, as long as the bike handles well for you .
The habit of the bike wanting to go right, may be a result of the 'crown' that a lot of roadways have built into them for drainage purposes .