You have no idea how memory management works in both OS'es. Linux on default will cache as much as possible just as Windows. What's the point of having 32GB of RAM into your computer if your not going to use it? Exactly. So you use it and release it when you actually need it.
Linux is very good in caching as much as possible - once you need the memory for for examples ongoing programs or games it will automatic be released. I have 15 servers based on Linux, in 99.9% of the time all the ram is consumed, as it should. It's all caching resources which makes the box obviously faster.
As for gaming performance, unless the modder managed to crank up the frequency's, there's no point in doing this for performance. I doubt it - these where likely replaced with double the capacity.