Final Fantasy creator Hironobu Sakaguchi has revealed which game in the series he thinks is "most complete," and it's not the fan favorite Final Fantasy 7.
Of course it's not FF7. Every FMV used different models, half of the second disk has dialog for Aerith, the weapons (that you fight) felt like half a battle each, and the story was an absolute mess.
It's still the best one, it just felt like it had so much more potential.
Are you talking about the chibi models vs. more realistic models? I think that was an artifact of an FF trope left over from the NES era where the world sprites were limited to one tile due to NES hardware limitations while the battle sprites were more detailed 1x2 tiles, and this was kept all the way up to FF6 where they finally used the same sprite for world and battles.
I have no clue why they went back to using different/less detailed models for world exploration in FF7 (if I had to guess they were unfamiliar with the PSX hardware and the chibi models used fewer polygons), but that go a long way to explain why the FMVs sometimes used different models--IIRC, the FMVs with chibi models played directly from the field, and the ones with more detailed models had some kind of scene transition into them, or otherwise were used for major plot beats. It's good they abandoned this entirely with FF8 onwards, though.
The more simplistic models being used with the FMV backgrounds was done to keep the framerate of the characters high while the PSX was busy with MPEG decoding.
Also, if you go looking at speedruns and people who look at the code, this game is held together with spaghetti code, bubblegum and duct tape. So easy to just break something.
Original FF6 broke easily as well. There's that girl character that has that ability to paint monsters and then mirrored versions of the monsters attack for you. Often the game was left in a corrupted state and crashing after a while. I usually loaded a save immediately but once the last save was a long time ago. I managed to enter a cave, a town, or something. Loading fresh data meant the game would no longer crash. All my item inventory slots were filled with random trash, though, which I sold to get rid of. Afterwards I had so much money, I could max out my equipment, potions, etc.