One of the tenets of the PBR workflow is that it should hold up under any (reasonable)lighting setup - provided you don't push your values too low/high. So changing your maps to suit your lighting shouldn't be required as it once might have been with the older diffuse/spec workflow.
Scratches would be mostly in the gloss/roughness map, and which values you would use will generally be determined by some simple logic. First, ask yourself what the properties of the base material are? Then, consider how those properties would change if you scratched into the surface of the material. Assuming you have a…