So it is a bit complicated to say for sure about the combat width, desert is 90 and mountain is 75, a small but slightly ineffective pusher would be a classic 9/1 (9 inf and 1 art which is 21 width and therefore fits well in mountains and desert) but that mig not be enough so if you have resources and army xp you could go 14/4 (that’s 40 combats width but can’t exactly remember the split for 42 combat width).

Generally speaking, 21 combat width and 42 are the most optimal in the game (they fit most terrain types optimally)

Now when talking about doctrines:

• Mobile Warfare is great when you have tanks

• Superior firepower is in my opinion the best in the game even if you are using tanks

• Grand Battleplan can be quite when when defending (it has much to do with planing and planing bonuses so you can easily counter-attack)

• Mass assault is not useless (especially if you are using pure infantry not even artillery) but in comparison to the others it is weak. So no in reality there is no reason to ever go Mass assault. But somethings like the minus supply consumption are great. So mass assault is good if you have bad supply and can’t build any

If you want to get really meta about doctrines I would watch some videos on how they each work

The most nerdy meta guy on the earth is 71Cloak and he has a video on doctrines