About some of the changes in 0711:
There is some per-track housekeeping for each track panel/mixer panel that is done, and if you resize a track panel or scroll it ends up having to adjust these things. dev0711 optimizes these cases a lot. It makes a bigger difference on Windows, but here's an example gif:
http://1014.org/_/reaper_5980_vs_dev0711.gif
With 500 tracks it's a pretty huge difference in UI smoothness... the difference is still there on macOS, though it is less pronounced.