Using CC2018 I thought I read that when you mouse over a preset it displays a preview of the how it will affect the image in the Navigator window like in previous versions, though it will also do it in the main window. Is this true? If so, how do you turn this feature on?
You don't turn it on. It is on by default, but you must be using 7.3 or newer. It's an odd question because some people have been asking how to disable the feature.
Does it slow performance down? What do people seem to dislike about it?
Apparently it slows some systems down significantly. I'm using an old HP Pavilion desktop, and I haven't had any problems.