I tried to look for this but don't seem to go anywhere.
How do I disable the subtle transparency that it affects out of focus windows? I use multi monitor and since I can be on focus on one app at the time in Linux, this effect put me off if I need to read something on a window not actively used on the second display.
Sorry, I don't know...
Maybe you could try something in Windows Management -> Windows Behavior?
Eg. playing with Focus stealing prevention (I keep it to Low).