Welcome to the forum! Your picking looks and sounds great! BUT just like you say, the motion mechanic is totally different at your two different speeds. At slow speed you use forearm rotation and a downward slant, at fast speed it actually looks like wrist flexion and extension and more of a upward slanted motion. I can be wrong here. But anyway the rotation is gone.
This is not a problem at all if you work with it. Let’s assume your fast playing is UWPS then there are a lot of great fast licks that use just that picking strategy. On the other hand, if you want to keep DWPS, then you may benefit from working more on your rotational technique.
Being a “CTC-convert” that discovered the rotational playing style via Troy, I can say that I had very similar problems when I started converting to rotational playing. At fast speeds I reverted back to my old wrist motions that for me wasn’t as smooth.
I think if you want to maintain the rotation at higher speeds you need to maybe use more edge picking. Angles was and is something I experiment with a lot to get the smoothest feeling attack. Also I would try to gradually raise the speed to see where the motion changes from rotation to wrist. I guess there is a point where the body wants to change. Maybe you can work with keeping the rotation there. The motion for me at my highest speeds feels like shaking you hand in mid air. It’s a totally relaxed and natural movement.
There is a resent thread called Qwertygitarr’s picking motion where I discuss a little bit about how I play and how I think about this style of playing. I’m not sure it will help you, it might not be what you’re going for, but it’ll show one way of playing.
