Shader performance & LOD shader

I've 2 questions. Well, both are shader related, but different.
Q1: Which one of these two will give better performance? Self-illuminated Diff/Spec/Bump OR normal Diff/Spec/Bump with a separate independent light. Better to inform, all of them are Unity's builtin shaders.
Q2: Is it possible to write a custom shader that supports LOD? i.e. If the mesh on which the shader will be applied is near the camera, the material will be parallax_diffuse. Staying a little far from cam will make it having bumped_diffuse. From the furthest distance, it'll have just plain diffuse. I think it could be achieved through sub shaders but not that sure.