Yes and no. Currently, the rooms are seperated (stock) and the game only renders the one you are in, but when a mod like this ties them all together then it's very much possible that a limit is reached at some point. That limit is undefined... We just don't know what the engine and our systems can handle. And although modern day GFX cards can distinguish invisible parts quite well themselfs without any optimization, it will always do more than it may have to at any giving point if the engine keeps doing unnecessary draw calls.
Animations add alot of overhead, as each frame is a new mesh slightly altered from the previous one. They all need to be loaded/cached at some point to allow smooth playback...
Mikhayl, lightmaps do not really add alot of performance hit, but lights do. They require extra passes (one or more per light), while lightmaps are blended with the diffuse in a single pass. That's why lightmaps were invented.
