So recently I upgraded my iMac 4K (2017) from i5 7400 to i7-7700K (delidded), also went from 8GB to 32GB of RAM. I noticed that everytime I export audio in DAW, the temps are growing up to ~ 80°C and system is lagging very much. I can't even move the cursor. What's even more the power supply is...
So as has been well established on several threads here and elsewhere, the 2017 27" iMac with the Intel Core i7-7700k experiences extreme temperature spikes, and can have sustained CPU temperatures of 95 - 100 C when under heavy CPU load.
I have one of these iMacs. I don't care in the slightest...