I recently bought the Rockstar Launcher version of this game and thought that my PS4 controller would be compatible without configuration.
As it was not, as I have a steam account I decided to try doing the following.
If you have steam, add the "GTAVLauncher.exe" as a shortcut in and open Big Picture mode. Open GTAV, log into the Rockstar Launcher, and the PS4 controller will be mapped and ready to use without other requirements.
If anybody else can confirm with EGS version that would be great.