I've never used #3 (I need to get some though). I've been working on the headlights of my Civic with #2 lately. Personally, the scratches don't bother me all that much. It is the cloudiness and yellowing that the Novus will fix up.
How bad are your scratches? Are they normal wear and tear, or knife gouges? Novus doesn't really remove scratches, it really just removes material to get the surface down to that level. If the scratches are deep, you are SOL because you'll wear the plastic down to nothing.