I agree RAM speed don't make huge differences in normal use.
Also your OC'ing the IMC thus could limit CPU OC.
But when I was buying RAM 2400Mhz was about same price as 1600MHz so thought why not?
Recently did a bench in XTU with XMP off thus RAM @ 1600MHz, score = 840 points.
Switched on XMP, RAM @ 2400MHz instant 200 increase at same CPU speeds.
So depending on what you do with rig does make a difference
😉 .