If there's a topic that gets more debate than is needed it's the topic of Squats
How wide a stance?
Feet turned in? Feet turned out?
Front Squat or Back Squat?
Look, no one cares!
All we care about is if it's making you better or not?
Is it moving you closer to your goals or not?
Does it hurt or not?
So, how deep should we squat?
Short answer: As deep as you safely can.
Slightly Longer Answer: The squat as a strength exercise can be done to whatever depth is comfortable for the athlete. There is no absolute depth outside of Powerlifting competition. And if you watch enough Powerlifting videos, even that is debatable!
Taller lifters, may have a hard time if they have long levers, particularly femurs. There's the individuals hip architecture which may or may not allow deep squats. There's bar placement, in that front squats in general go deeper than high bar back squats, which go deeper than low bar back squats.
As a movement, rather than an exercise, the squat should be as deep as the person can manage safely, without pain. As a movement, it's worth taking the time to gradually improve the squat to allow a full resting squat position, something we could all do as kids, but lose as adults mostly because we stop doing them.
But as a strength exercise, there is no absolute. I would suggest getting your full range of motion strong for a joint health perspective, but for an athletic performance perspective, if you're hitting parallel, you're going to be alright.
The critical point to avoid is to ensure every rep of every set is identical regardless of load. Don't be the guy who warms up with full squats but then loses depth each time he adds weight to the bar!
What Squat Stance Should I use?
Short Answer: The one that allows you to move best, to load the body in the manner you wish.
Slightly longer answer: The squat, like many lifts, can become an ego lift where lifting more weight comes above all other factors. But please don't lose sight of why you're squatting in the first place.
I dare say it's to do with getting strong, putting more power through the ground/pedal/opponent and maybe a little bit to do with bigger quads (check out the quads & glutes on your favourite powerlifter, hardly impressive when compared to a bodybuilder...) To this end, I encourage athletes to squat in a stance that is between hip and shoulder width. Simply because this where you're most likely to be aligning yourself in the performance of the sport. Once we start in this middle ground position, we then observe to see if they need to be a touch wider, a touch narrower etc. Their body will tell me, simply be observing their mechanics. Your body will tell you if you simply tune in and learn to feel how the weight is distributed in your feet. Can you keep the weight in the middle of the foot as you squat? Is the heel loaded, is the ball of the foot (1st and 5th knuckles) loaded? Is it the same in each foot?
As a general rule for alignment, wherever your toes point, that's where your knees will also point. Hopefully this nullifies the arguments of whether the feet should be pointing forwards or outwards.
Squatting isn't complicated unless you want it to be. Hopefully this simplifies things for you