Mods only affect graphics, sounds and user interface. Mods do not effect weapons, units or damage or anything like that. What mods would I use? Right now I only use a few. Grid lines on terrain. This helps me see contours in the landscape.
The other one is the empty sound file for the opening music.
Gustav Line adds the additional time frame. This provides units available at the designated time frome and contains additional types of terrain features for that part of Italy. It also provides the additional battles.
And one more thing: I'm not an expert just a player.