Both are the same except for the initial form. The ImPRESSive Putty MIX needs to be heated prior and MIXed prior to it's first use. The ImPRESSive Putty (no mix) is already mixed together and you just heat and press. Both are the exact same material. After you mix the MIX it can be re-melted and re-used as many times as you like to make lots of different mold shapes just like the pre-made ImPRESSive Putty. You do not need to add anything to either. 

Can I use my regular dishes to heat the Putty? 

Yes, the ImPRESSive Putty is food contact safe. This will not damage any plates or dishes. If you have any on, just wipe it off or wash it away with hot water.