hello.
Probably better off discarding the term "buttwink". Also read the sticky about preferred video angles / camera positioning (further back and lower down being prob the most important).
From these camera angles and to my non-expert eye your squat looks generally ok. Your low back looks ok.
For the "front" set. Look down more. Also your knees continue to move forward all the way down. You should establish your knee position early in the movement so that that in the bottom 1/3rd of the squat there's no back and forth movement of the knee both on the way down and the way up.
In the second half of your "back" set your knees are moving in a fair amount on the way up. Focus on pushing them out.