It really depends on what kind of cooler you slap on that chip that will dictate how high you can push your voltage. You might want to consider a delid if you have a less capable cooler.
I have an i7 7700k and an MSI Z270 SLI board, no delid, so similar to what you are running. With my Noctua NH-D15 cooler I was only able to get 4.6ghz running stable at 1.25v with temps at around 80C at full stress load with Prime95 and IBT. I tried pumping in more voltage to get to 4.8Ghz but for the life of me could not get it stable. Its a tricky chip to be sure.