After the update of deepin-mutter (3.20.7-1 -> 3.20.8-1) it is still the same. But switching to deepin-metacity (Super+Shift+Tab) makes the CC appear fast and uses just 10-17% CPU. So, probably not a critical issue. But I also prefer the previous look, now it looks just like Gnome, it is also too transparent with deepin-dark theme.
The new budgie-desktop doesn't have any obvious changes in user experience, thus no issues. Will test lxde-gtk3 next.