Some guys have stronger glutes than quads and some have stronger quads than glutes, typically leg position during squats doesnt change much due to balance issues but during lunges, leg press and deads you can move your feet around, esp during leg presses where your in a fixed range.My issue is where to point the toes. The squats feel best when my toes are pointed more aggressively outward. Much better on my knees for some reason.
If your feet come really far forward and apart its mostly glutes if your feet are together and under your ass then its all quads but can be brutal on the knees if you go super low.