I have been modding GTA IV and GTA V for some time now. Lately I've got back into modding V since the content has improved drastically. What I do not understand is what is the purpose of the Vehicles.meta, Flags, and Carvariations files. So far I have modded just about every police vehicle in the game and that includes renaming the car files to suit my needs. I have had zero ill effects on my game by ignoring the files mentioned previously.

What is the big deal if it doesn't harm anything that I can see? I remember from IV if you didn't mod the lines correctly the handling and other issues would show. I use notepad ++ for editing needs but is there an easier way to update the vehicles.meta, flags, ect as you download and swap cars?

Maybe I missed in while searching for an answer.

carvariations allows for livery/colour differences (and probably other differences). Vehicles.meta defines things like the interior used, the handling line it'll use, and probably some other stuff. Handling.meta defines the actual handling lines that vehicles.meta points to (eg, you can have a single entry in handling.meta for a granger, then in vehicles.meta use that handling line for the granger, sheriff2, fbi2, pranger slots since they're all different versions of the same car).

If your cars work fine and handle ok in game, you can probably get away with not including meta lines for them - just make sure you list which vehicle slot they're designed for (ie, the one you tested in and worked fine). If you're using the police slot for example, and I install your car to my fbi2 slot for some random reason, it's probably going to drive badly. The most common handling issue I've seen is with vehicles needing their mass / center of gravity tweaked, which is evident when trying to turn at high speed and the car goes flippity flippity flip.

Thank you. That all makes sense now. I suppose I've been very lucky so far. Though I try to match modded cars to vanilla car slots. So they drive normal.