The thermal compound application on the 7700k is subpar at best. De-lidding and re-applying can make a huge difference.
The CPU also exhibits very high spiking, so your max values will appear to be high, though they aren't sustained for long. Even with water cooling I was getting the occasional low 90s, but the CPU seemed to actually run closer to the low 80s most of the time.
After de-lidding the highest spike I have seen is 78C, but more commonly in the low 70s.
What you should be looking at first though is the CPU core voltage. The defaults will probably take it fairly high. I believe mine booted at 1.35 which is quite high for the stock settings most of the time. 1.4 being the safe max with good cooling.