Overclocking on Kaby Lake-X is not all that hard at all if you are familiar with Intel overclocking. We are not going to go into much detail here as we plan to do a follow-up article, but we were able to get all 4 cores of the i9-7740X at 5.0 GHz.
This processor does not get as hot as the i9-7900X, obviously because you have 4 cores going instead of the 10. Our cooling was the NZXT Kraken X52, which did a good job cooling. I feel we could have got a higher overclock with more time and better cooling, but 5.0 GHz is pretty good, and you could run that overclock 24/7 with no issues at all.