The apps were snappy, but the hardware wasn't. Every menu/window opened immediately and without unnecessary animation... unless it needed some unexpected processing - then you were potentially waiting for the spinning rust to handle the swap file.
Also, it’s pointless to open a menu in less time than it takes the screen to refresh.
No, that would be the goal.
Once should be quite enough.
https://userbase.kde.org/Tips/Enable_fun_desktop_effects_on_...
I am pretty sure this is good old resistance to change. You would disabled them on all your systems, then force yourself to use them that way for a month and I am pretty sure that "disorientation" would quickly disappear.