Only a short number of files (sky and grass, if I remember well) are substituted. In such case, any other mods in the same installation will have the new sky and vegetation textures (and a backup is saved during installation). Nothing more.
Some of the fans (and developers ) have several mods including ITW in the same installation. Only be sure that the other mods are also using their own mod folder.
@Artaserse
It's really rewarding for a developer to find a fan like you.
And.... yes, we tried to get as much realism as possible in different aspects: casualties and their origin, lethality of weapons, sounds, different horses... Glad to see that at least some people remark those points.