Wow, this sounds really interesting. As someone who used to be an avid GTA V player, I can imagine how much fun this can be. Do you have any videos on the mod and/or on the playing experience?
FiveM is the most popular platform for this type of modding, and is the one I use. nopixel is the most popular server on the platform and usually a good place to start getting a feel for what's possible on a modded GTA server.
If you check out https://nopixel.hasroot.com/, they maintain a list of all Twitch streamers currently streaming nopixel.
