Gnat,
There is no "pat" answer, most people who use a reference system, such as gap, split vision, etc...often times prefer a bow that is vertical. Having said that, even some of them will cant a bow to an extent.
The things related to form, have very little if nothing to do with the degree by which a shooter cants his/her bow.
It has to deal a few of these things that should not change regardles of what type of bow is being shot. 1) consistant grip on the bow. 2) a slight push on the bow toward the target. 3) the elbow of the drawing hand should maintain a straight and level alingment with the arrow, and if viewed from the above, the arrow, the drawing arm should be in perfect alingment. 4) a rock steady follow through with no arm dropping until after the arrow hits the spot. 5) a continuous line of energy, with the drawing elbow with tension away from the target, and the bow hand pushing slightly toward the target.
I may have missed a thing or two, but these are the things that should be focused on as far a form goes. Regarding the angle of your bow, find the most comfortable one and stick with it. Oh, by the way! I have seen a lot of great archers, that when you watched them shoot, you would say that their form really was bad. The thing that made it work for them was the fact that they did the same thing on every shot. I guess if the arrow goes where it is supposed to on a regular basis, you gotta be doin something right!
Good Shooting my friend.