This is just my settings.xml file. Not sure if you can use it online or not.
All of the settings are set to max so make sure your computer can handle it or it will crash the game.
Installation: MAKE A BACKUP OF YOUR SETTINGS.XML FIRST!
Unzip and place settings.xml into your “Documents/Rockstar Games/GTA V/” folder.
If you would like to make changes to the city density, ped variation
and vehicle variation just go to “Documents/Rockstar Games/GTA V/
and edit the settings.xml file in these locations:
(Setting the values too high will crash your game, these are the
the lowest I was able to use before my game kept crashing, but I
use a lot of mods. The default values are “1”)
If you would like to just keep your game settings, but increase peds
and traffic just edit your own settings.xml file in those locations.