I have couple questions on form.

Should I switch to full squats from traditional squats? I've heard that going past 90 degrees at the knee can be damaging on the knee but I don't know how accurate that information is.

On deadlifts where should I have my arms in relation to my legs? Let me know if I'm right when I say that traditional stance has knees inside arms and more a sumo style has feet far out with arms inside knees. I'm asking this because I've had some trouble with my arms conflicting with my legs and I was wondering if maybe I need to bring my feet in a little bit and my arms our slightly.