Thats a loaded question I have delt with for years in training fighters. The best answer is ..."it depends"..
The key of course is getting the body weight behind the punch, and the turning of the foot depends on your size, weight, body structure, stance, balance, and how you return your punch back to the guard position. You are trained to turn the foot enough like a twist ..........only as far as necessary to swing the body behind the movement for maximum power, while keeping your balance. Bottom line... that depends on you, and your trainer observing and evaluating.