@chonkie
I'm not sure that is the issue. Because as I stated above, I downloaded a gameconfig mod (https://www.gta5-mods.com/misc/gta-5-gameconfig-300-cars) which involves me dragging and dropping an edited version of gameconfig.xml and replacing the old one, and it gives me the same crashing result. (the game worked fine before it was installed)

Whatever the issue is, it seems to stem from the game not wanting me to edit these xml files for whatever reason.

Several mods I have tried required me to edit the dlclist.xml file in OpenIV in order for the mod to work. Examples being:
The dismemberment mod
https://www.gta5-mods.com/scripts/dismemberment
and this army vehicle mod
https://www.gta5-mods.com/vehicles/m1114-up-armored-humvee-add-on

When I edit the file, they ask me to add some stuff to this text file. In the case of the armored vehicle, "<Item>dlcpacks:\uparmorhmvdes</Item>"

So I take the file out from OpenIV, make the change in Notepad++, and insert it back in, replacing the old one. Then when I go to launch the game, I get greeted with a pop up that says "Corrupt game data. Please reboot, verify the game data, or reinstall the game. For more information, please visit: http://rsg.ms/verify"

Verifying the game files (on steam) does fix the problem, I assume it reverts dlclist.xml to its unedited state. But it leaves me with the issue that I can't install the mod. Any suggestions? I'm running the latest version of GTAV and, I'm willing to provide more info if asked.

Another note; yes, I tried the gameconfig.xml modification. I got the exact same result as above.