It depends on what your definition is for all of your qualifiers - these mean different things to different people. Your best bet might be to try a handful from different developers to see how they meet with your needs. Raw Power from Gentlemen Coders (ex-Apple, Aperture developers) is powerful, fast, minimalistic from my perspective, works on Mac OS and iOS devices and can work as an extension to Apple's own Photos, which is also, for what it does, reasonably fast, powerful and minimalistic.
Tools like Luminar (Skylum), ON1 and the like are less minimalistic but have lots of one-click filters for "instant good looking images" (saying somewhat tongue-in-cheek as it depends entirely on what you think of as good looking).