The speed of the RAM is more important than size for games, at least if u have 16GB or more. Fallout 4 VR gains extra fps from fast ram, but thats also one of the few CPU demanding VR games. Some simulators might me an exception.
But to be honest, its a very bad time to upgrade RAM with the current prices. As long as u dont video edit, photo edit or do some heavy workload then 16Gb is fine.