- Best light build result depends on many factors I think. But the tools that I find most useful in ‘debugging’ my levels and speed up build time is Lightmap Density (press alt + 0) and Lighting Build Time [build button (down arrow) -> lighting info -> lighting static mesh info -> light build time]. Lightmap resolution of 256 sometimes is enough to produce better/smoother shadows and also it’s 64 times faster to build than 1024 resolution (according to DanielW, the UE4 developer)
Don’t forget to always fix overlapping lightmap UV error no matter how small the object is. I found that if you get more than one of this error (meaning multiple objects have overlapping lightmap UVs), they could slow your level down while ‘playing’, and they also make UE4 to always re-cache the lightmaps and this caching process causing pauses in the editor and inside the game. Not to mention longer build time.