This video is quite interesting, because @pcho doesn’t always use a panhandle overhead! There’s examples, especially in the second half of the video where he is using pronation/supination. 1:18, 1:26, 2:07 are some examples where there isn’t as much panhandle going on. The backhands even show better technique than the examples at 0:18, 0:23.
@pcho – are you aware of the differences, or are you trying something out that someone tried to teach you at the start of the video? e.g. wrist/finger power or something to that effect? It looks like you are trying to bring in a new technique in the early parts of your video, then you ‘regress’ back to a more pronations/arm based swing once you get warmer or more competitive.
One thing that is very clear is that you panhandle and use a wrist ‘snap’ that risks injuring your wrist on your high serve every time. There is no stroke in badminton where you want to allow the power of the racquet to be stopped by the bending of your wrist. It should be dissipated by the rotation of you forearm.
Echoing the others, your footwork and positioning is really strong compared to your overhead technique. If you adjust your grip away from panhandle (rotate it roughly 30-45 degrees clockwise in your hand), you should find you can get better angles (steepness and hitting to your left) that you currently struggle with. Your panhandle grip is leading to you necessarily taking the shuttle lower than you could (flatter shots), with less power, and more strain. This is a shame because you are regularly moving into a great position to hit as well!
