Thanks all!
I'll practice slow to get proper technique and will practice with 2.5 lbs slowly to just raise my knee. So Yak Sao, that 2nd vid you showed above is what you mean by
chamber our kicks but just raise the knee? It's more of a step and kick? via 'step to kick and kick to step' ?
et al, so to raise the knee and chamber, while leaning body back for balance, then kick and retract, is only for a massive power kick to push?
But Yak Sao's fast, 'snap' kick is more for speed, surprise, efficiency, it seems. Which is the Wing Chun way.