Well, TSL probably would not be able to do what KOTOR did exactly. To some extent, it did have slight differences in terms of lighting. It wasn't exactly duller, but might have been a dark game. (Many parts of TSL did not have exactly bright lighting effects) Besides most kinds of lighting in K2 were more like neon lights, like in Telos' cantina, on signboards against walls. Put simply, there were small sources of light rather than bright ones being used.
Some points:
K2's Sith assassination story was executed poorly
NPCs were few
And also modified lighting that K1 used