If you're still answering questions:
@DevM
How do you correctly guess, or make a safe guess, about where your opponent will attack if you're relying on highly defensive play?
For instance, what is your mindset when you place AT guns somewhere in the map to anticipate a light tank rush or any other tank?
Most of the time you can hear the vehicles in the fog of war and move accordingly, otherwise I just place the AT guns in a central position so that they can quickly move to one of the sides. If you are talking about infantry instead of vehicles usually I try to keep my units mobile and avoid playing defensively since it gets hard to guess where he will come from, if you have your units moving somewhat close to each other you always know where he is coming to come from since he will most likely try to stop you if that makes sense. Also poking around with some infantry units is always good, never go fully on the defensive.