I'm having a hard time finding information about this. I have just finished several new competitive maps and I am going through the mundane tests right now - firing up a second controller and just making sure the spawn system is fine, objectives are in the right place, and looking for framerate problems. I'm hopeful that at least two and maybe all three of these will be playable in splitscreen, which wasn't the case for a couple of my old maps. What I noticed was that I was able to run around in splitscreen just fine with no noticeable screen lag spikes, except for when I was testing the location of territories (and possibly also hills). When I was approaching or inside a territory, I was getting some minor framerate issues. Nothing game-breaking, but obvious and kind of annoying. Is this a known thing? Does the rendering of the hill or territory perimeter contribute to framerate problems, and if so can I really do anything about it? My maps are already almost as economically designed as possible except that one uses two lights and the other uses one. It would be hard for me to simplify their designs much more. I'm thinking this might be something I just have to live with, and assume that it likely won't happen on fullscreen mode anyway.
Hills and Territories, or any objective that puts up a transparent barrier will cause framerate drops. Glass causes framerate because you have to render objects on the other side of the glass as well as rendering the glass and th color changes it produces on the object you're seeing through the glass. Same concept applies for any translucent object.