Mr. Surfacer 1000 contains finer granules than Mr. Surfacer 500. Mr. Surfacer 1200 contains finer granules than Mr. Surfacer 1000. Surfacer 1500 can be applied to give a final finish to the surface more smoothly.
I build model cars and use Mr. Surfacer as my primer for all plastic and resin parts. It adheres well and sands smooth. I've never had it react badly with the paint.