If forced into a 'typical' choice, I'd say 'homebrew, very different, loosely sketched.'
Spelljammer is a sort of hybrid of homebrew and published; you can GO to the published settings, but probably won't stay there, there's lots of homebrew stuff to explore, and the flavor of the game and what's out there diverges rather wildly from the norm. In 2e I would have called this 'published, loosely sketched, moderately changed' - although by the end, I played it with Rules Cyclopaedia rather than AD&D, so it was a homebrew even then. Since I advance the Spelljammer timeline by about 50 years, even a lot of the setting elements are heavily changed.
Ivalice, although based on existing source material, was definitely a homebrew. For the sake of the setting, it had a substantial amount of restrictions and changes (no elves, dwarves and the like, goblins were changed but playable, etc.), and because of the aspects I played up, magic was rare and dangerous (ala Vagrant Story more than FFT) and guns were available (from Romanda) and heavily employed.
Animus War drops the non-human races, incorporates mecha and superhero-like powers (albeit the latter in a heavily restricted fashion) and has a completely homebrewed monster suite. It also has firearms and is based on more of a d20 Modern/Past core than D&D, albeit with elements of both.
I don't flesh out the details of any of these settings before play. In Spelljammer, it's simply impossible to cover the territory available, so I usually just have a stock of concepts to explore as the PCs wander the known spheres. The others I handle similarly - sketch the nations/regions and their customs and go from there.