Ok so before building lights if you place objects in your scene they get a standard dynamically lit look… but they won’t look realistic because of the lack of GI… If you use static or stationary lights then you’ll have to build your lights and your static meshes will get GI information too…
Every mesh has to have a uv map for (baked)lighting information! Even if you don’t have textures! Imagine it as a “lighting texture”. Without it Unreal won’t be able to visualize the lighting for you!