the only thing the shadowgraphic settings affect are the real-time shadows, which are used for dynamic objects (debris, prop_dynamic, players, physical objects, buildings). The shadows are only affected by the shadow_control entity, and imo look pretty bad and dated for reasons I mentioned in my previous comment. Setting them to low looks a lot better imo, but as a mapper you should still care about the shadow settings in your map since most people play with shadows set to high since they aren't very demanding.
Maybe I'm just too nitpicky but once I saw the shadows overlaping I just couldn't unsee it thats why I set them to low. well, It's old tech from HL2 after all