On intel platforms the amount of ram and speed of ram have little effect on total performance. On Ryzen and probably Threadripper systems Ram will play a more pivotal role as the infinity fabric's speed it tied to the ram speed so faster ram would yield faster core-core communication. That said so far infinity fabric clocks have been pretty static. 1-2% on intel, more on AMDs latest platforms maybe more.
Unless, as Supahos says. you are actually using all the ram you have available. If you are using all the ram then installing more could substantially increase the speed of they system as it would have to reference the pagefile on your storage device.