Some have issue with this setting.
But it is supposed to be a good middle-ground where if you are running a game for example it turns off the compositor.
If you dont want that setting … you might be able to get by with just leaving the compositor on … but that is a rareity … rather its mostly this setting, off, or replace compositor (and probably implement a similar setting)
PS - it seems very little is different from your above setup besides OpenGL version (you still might prefer 3.1).
Which also leads me to believe that there were larger/lower/fundamental issues with your previous install.