I released a mod to set the battle FPS to 24 and the booster speedup to x2
in the FFIX OT as well, but to be fair I still think that's too fast. The reason why I made that mod was because everything looks really choppy when the battle FPS is limited to 15.
To be fair I think the ultimate release of FFIX would have battle FPS on 60, but the actual speed of the battle system and the animations the same (though interpolated so it isn't choppy anymore). Those who think the animations are slow can just speed it up with a x2 booster or something, but anything more is crazy and I would personally play most of the game without booster (yes, I don't mind the 10 second camera pans).
The PC release sucks for other reasons though - I hate literally all of the changes they did to the UI since the PSOne version: it's too large (designed for smartphones and never adapted to PC), it flickers at times (the text balloons), etc. So as it stands, the PSOne version is still my favourite.