How do you use it? Supposedly I need to use the playgtav.exe file, but I don't have that in my Steam directory, just GTA5.exe and GTAVlauncher.exe.
Install SweetFX/ReShade into the following directory = \Steam\SteamApps\Common\Grand Theft Auto V\
taken from here
https://sfx.thelazy.net/games/game/938/
its another preset, but basically extract the sweetfx folder into the GTA 5 folder you have. inside the sweetfx folder there is a config file called Sweetfx_settings.txt. take the preset config you want to try and rename it to that and replace the default .txt file.
also make sure the ReShade64.dll is renamed to dxgi.dll and also placed in the GTA 5 folder. check the readme inside the Reshade 0.18.0 release for these steps but thats the main work you have to do!
thats it. enable/disable Sweetfx with scrolllock in game.