It increaes the 1% lows, so your minimum fps is increased. Max fps is not so important.. if you play with 144hz its just important to not go under 144, so you might not need high freq ram for that, but if you play 240/360hz it most certainly matters. Honestly the difference was bigger than I thought. Had 2x8 3200cl16, kinda crappy hynix ram (hyperx) that couldnt oc.
System felt sluggish and I wasnt happy. Then I got 2x8 oc to 4000cl15 and god damn the difference.. it feels like the monitor and the mouse moves waaay smoother. Faster, snappier... worth the investment imo.