I take my quiver off when I am on stand.I practice with it off.Having a level in your site should remedy any canting.
I just read an article in one of the archery magazines (Bow and Arrow Hunting) I think.The author said there was no practical difference in point of impact out to 40 yards.
As others have said though as it relates to consistency you want to practice the same way you intend to shoot while you are hunting.