I would agree with them that you are best to stick with 2GB, but it depends on your usage.
You can utilize 4GB of RAM with 256-bit bus width, which I am not sure the 760 is 256-bit bus width or not. Not important, but you if you are running for example a 4K resolution or multiple displays you might want to get the 4GB version.
Two of the biggest uses of the RAM is on higher resolutions and multiple displays, because it has to hold so much more information before it is displayed.
If you are doing a single display at 1080P or lower, 2GB is plenty.