Okay, I found out something testing different lightmap sizes. I tried a single wall with two windows and a door on it. I had to increase my lightmap to 1024, otherwise the shadow quality would be poor. So I decided to break my modular wall in one wall, one window and one door, separately. I decrease lightmap to 64 for each piece and downsize the texture from 2048 to 1024 (each mesh). Adding the meshes in the level, I checked the status and actually all the numbers went down (lightmap and texture RAM usage). Not always many objects mean a performance drop. It depends on the poly complexity, texture size. My doors and windows were simple because the level was inspired on a small Venice city (everything is a rectangle basically XD). I don’t know if the same logic applies to complex meshes.