FYI CS:GO is very CPU dependent and will improve in performance with a CPU overclock. Are you running stock 3.5GHz speed on that 4690k? Getting it up to say 4.5GHz with a good cooling solution will show improvements in FPS drop areas of the game. However, like everything else in the PC world, a boost of your GPU overclock can help too in combination with the CPU overclock.
Also here's a good Steam guide to ensuring you are getting as good a performance for your system as you can for CS:GO -
https://steamcommunity.com/sharedfiles/filedetails/?l=norwegian&id=268030869