I do remember that very few, if any of the mods I tried to use for DS2 worked right with the DS1 in DS2 mod/maps. I assumed this to be because DS1 in DS2 is such an overhaul style mod that it forces incompatibility with anything else. Mods that change pretty much anything about the vanilla DS2 experience would likely be incompatible, because what they change is already changed to get DS1 in to DS2...
Testing this could be a matter of trying the game without any mods besides DS1 in DS2. If it works right (exp gain) then add mods until you break it.
I do remember that very few, if any of the mods I tried to use for DS2 worked right with the DS1 in DS2 mod/maps. I assumed this to be because DS1 in DS2 is such an overhaul style mod that it forces incompatibility with anything else. Mods that change pretty much anything about the vanilla DS2 experience would likely be incompatible, because what they change is already changed to get DS1 in to DS2...
Testing this could be a matter of trying the game without any mods besides DS1 in DS2. If it works right (exp gain) then add mods until you break it.