should I let my sourdough loaf proof in the fridge or on the counter? I've been watching tons of videos on making sourdough recently, and quite a few say to let the sourdough loaf do its final proof, or rise, in the fridge. Is this necessary? Would it speed up if I just let it rise on the counter? Thoughts?
Speed is not the point. Speed is the opposite of the point. Refrigerator rising makes for a long, slow rise and flavor development - it's not unique to sourdough, it's very common in pizza dough (though not usually the "final rise" in pizza, as that would be very difficult to arrange enough fridge space for.)

You can do it, or not, or try both and compare.