They don’t really mean anything, they’re just things I made up to differentiate and have new names for some of my variations. They’re descriptive in a vague way. I would like users to more use their eyes to judge and evaluate things not theory. So go ahead and dig in. Use whatever you like.
Generally though Smooth use Scale FX and are upscaled. Sharp may or may not use ScaleFX but if it does, it will be at a very minimal level.
Pure, is, a relatively unmanipulated image, so little to no artificial upscaling for an experience that is closer to how real hardware might output to a screen.
I hope that answers your questions and do read the first post for information about these things and more.
Thanks for your interest.