test build

After build with the setting medium the scene became dark, is there any other other way to test the build to see the actual lighting before proceed to high or production build?
in foliage, whats that sparkling flicker appear from the foliage after the build?
please advise.

The only way to have an idea of your baked lighting before baking it in high quality is… to bake it quickly at low settings and see if the illumination is good enough.

But even with low lightmass quality settings, if the lightmap resolution of your meshes is high the preview can be slow to build.