There is no option to set the canting angle properly for your anatomy regardless of the A-frame. There is no cuff-angle adjustment option. There is no mention of the reason for the A-frame.
Your canting adjustment should be done in the shop so that your skis are running flat when you are in the proper position, or else in the position you are able to easily ski in. This is done by adjusting the bottom of the sole, making it slope the proper direction.
There is another, different, adjustment on some boots, my old Koflach Comp 911s for example, that allows you to adjust the angle that the boot cuff makes with the lower part of the boot.
It may be that your physiology forces you into an a-frame, if that is the case it would be easily seen in the shop.
As to affect on skiing, you first have to figure out why you are in an A-frame. You could be A-framing to make up for an improper canting adjustment; if your inside edges aren't low enough you compensate by bringing your knees in. In which case a canting adjustment is in order; a canting change that lowers the inside edges for a given angle of foot sole will then make it unnecessary to bring your knees in to make the inside edges low enough. You could be a-framing because you have some muscles that are more developed than others. In which case the above canting adjustment will only worsen the effect of the A-frame.