First off, I love your game. Wow. Blown away. I just came from mobile and a lot of things are different so far.
I can't pause and pre-set builds as my position freezes along with the pause unlike mobile. In mobile, I can actually move my screen and build in different areas (I may be remembering this incorrectly.
Also, I sent up my typical vent ammo ramps with junctions and they don't seem to work on PC while I know for a fact that they work on mobile. Here is a pic:
I hope I am misunderstanding something as I am very happy with my mobile experience.