Yes to all your questions and i squat both low and high bar.
gree with above poster, i dont think they will carry your squat nu,bers higher.
HOWEVER, they are really fantastic for mobility, shoulder stability, back strength (upper), balance, and they basically do all of these things at the same time. So i don't think that they help your squat numbers, but they help a lot of things that will keep you squatting longer and healthier. That in itself is worth a little time. Besides they help your shoulders get strong AND stable, which is useful for benching.
The basic rule of thumb is, if you can squat overhead with a med/narrow stance, it tells you that ALL of the joints are functioning optimally--t-spine extension is good, shoulders good, hips/knees/ankles good. And it maintains flexibility and mobility without a million prehab and/or mobility exercises after foam rolling....and i hate doing that so i use it frequently as part of my warm-up to get everything going faster. And my upper back warmed.
In that context i think they are very valuable as they do the job of several different exercises in one.