After reading your comment I started researching more this topic, and later watched bunch of benchmarks between 2133mhz and 3600mhz regarding in game performance. And fps difference was 10-20 depending on a game ( I always thought it would be few fps difference, which still is but in very few games) . So I decided to upgrade my ram
you can watch 10 different videos with all of them having 3600MHz sticks and all of them will have different performance
you can get more fps with better ram, but only if your bottleneck is CPU, if GPU cant keep up, there shouldnt be any improvement visible (maybe just on minimum fps side/less stuttering)
most memory modules can be manualy overclocked, what you buy marketed as 3600mhz is factory overclocked ram
as far as memory overclocking goes, it should improve gaming FPS, but not because of higher ram frequency, but because of cpu interconnect (uncore/infinity fabric) it overclocks alongside with ram frequency and that is main factor why higher clocked ram gives more fps, as cpu cores gets lower latencies from interconnect
ram frequency itself in games is mostly pointless, as most games preload stuffs before game even starts, so it may affect game loading time
openworld games might be different story as they keep updating scene as you walk around, but ultimately bottleneck there is storage (ssd/hdd), ram bandwith once again doesn matter that much, because theres also pcie between gpu and ram which creates another bottleneck to some extent, but most games can hide it pretty well
lower ram latencies and multiple available memory banks is mostly what matters in games, but if game has small code which fits in CPU cache, then ram doesnt really matter either
as mentioned above it depends on how is game coded, whether you need cpu with bigger cache or lower ram latency
but tbh you get more fps when you replace gpu then from ram
but if you need new faster ram, then go for dual ranked as they give more fps than single rank, while price should be similar