>What's the best versions of FF IV and VI to play?
GBA versions of both, unless you want to play "The After Years" content after beating IV, in which case you play IV on DS and After Years on WiiWare (PC/Steam port cuts out some content).
They're 'episodes' that combine into a full sequel, set a couple of decades after the original.
No idea, haven't played it. Have some random comparisons of the different localizations instead:
https://archive.is/Jkyap
https://archive.is/hjaFj