I believe it can affect your form, and probably does for many... but not necessarily. I find that more radical canting makes it more challenging to keep back/neck/head alignment. Also keeping string hand parallel to the string, and yes, expansion.
More difficult, but not impossible. I practice/shoot with varying degrees, according to the shot, including some pretty steep canting in the woods & roving. I shoot most consistently when I stand "straight" = though it's actually relaxed, with a slight lean. I pay attention to how my head, neck, and string hand stay in line with the bow. At 20 yards and up, I'm more straight up. I can't more as I get closer shots. If I'm bent way over (shooting under obstructions) I notice the increased challenges.
I'm sure as I gain experience, I get better with it.
And those who already HAVE way more experience than you or I will be along shortly to describe more.