You've already forked thumb-trackball
What's the difference between the two Tops?
The "-200" body has its ball well offset by 200um. This is to accommodate variations in ball size.
If you're looking to replace the Top that you got from an official Ploopy kit, look at the underside of the Top that came in your kit. If it has small shallow circular divot, use the "-200" Top. If it doesn't, use the "-0" Top.