Low Bar or High Bar?
To say a bit more, it's important that you can create a stable shelf for the bar that keeps you over your center of gravity. This is actually a separate question from the question of foot stance, though a change in foot stance may require a change in bar position. Generally speaking, wider stances tend to favor lower bar placements, and narrower stances tend to favor higher bar positions, but this is not a steadfast rule. Note too that bar position plays intricately into torso angle throughout the squat, and that if you are after a certain torso angle, this may influence your choice of bar placement.
Experiment, test it out, feel it, and change if necessary!
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