At least scrolling is improved on the M1. Some parts of GUI response seem likely to benefit from the faster memory access in the M1 architecture, but the rest looks like inefficient graphics handling in DP.
A partial workaround for switching edit windows, and the mixer is to switch to pop-out (Sequence editor and Mixer in my case), and leave them open. It seems they are completely redrawn/rebuilt every time they are loaded if closed, or kept in the consolidated window. I just use single-key commands to switch between, bringing the one recalled into focus.
This doesn't solve the impossibly slow scrolling through channels in the Mixer though, and the Sequence editor is still a bit sluggish to scroll through tracks compared to the Tracks window. And the Track Selector is still painfully slow in the Track window sidebar, and Mixer. Nearly unusable.
I also tested 300-audio tracks - similar results. In addition, zooming in and out is slow, especially during playback. Realtime load jumps to 50% with just one track of audio (the rest empty). 300 empty audio tracks sits at 25% Realtime load. No idea why DP needs that much overhead just to host empty audio tracks. No PDC, buffering or pregen would be needed. It seems to have a huge overhead just to load the GUI. Maybe it is time DP dropped the static graphics GUI and went with a fully vector GUI a la Cubase, Studio One, etc. I know that's easier said than done, and may not even be possible.