For these little white scratches, do they look like they go away when water is in contact with it? If so, then these are the kind of scratches that you could remove with GS27. Anything deeper than that won't have any effect.

Clay bar basically removes any contaminants that is embedded into the paint of the car (this includes paint overspray). When you wash your car and dry it, try sliding your hand on the paint. Does it feel rough? A clay bar removes these nasty contaminants by lifting it off the paint and onto the bar.

Make sure you use a clay bar BEFORE you use an orbital buffer or it might make the situation worst by smearing and grinding these contaminants into the paint.