Ok, first of all I'm no expert. Real Hdri do not need additional lighting, unfortunatly bryce does not support Hdri. A Lightdome is not necessary, you can do with just a couple of lights, but it helps. The sphere does not need to be transparent if you place the lights inside it. otherwise yes, a bit transparent. To round things up i really tink you should ask ornlu, he seems to know what he's doing.