Temps and voltage will be your limiting factors here. As a point of reference, I was able to overclock my 8600k, on an Asus Z370-E mobo, to 5ghz at 1.34v stable. Running Prime95 26.6 for 3 hours put my temps around 70. Im using a h100i V2 without delid.
I could push for 5.1 and probably still be below 1.4v, and I could probably get 5.2 around 1.41v. If I pushed to 5.2 I would probably have to delid. With that said, I was happy with my 5ghz and the temps I was getting. Under normal gaming load, avg temps were in the low 60s.
The answer to your questions, is one only you and your CPU can answer. Did you win the silicon lottery? Are you trying to push this thing as hard as it can go, or are happy with a hopefully modest OC with reasonable temps? If you cant get atleast 5ghz under 1.4v, exchange your CPU, as your CPU swung and missed.