A Noctua D15 performs almost equal to a top end AIO water cooler. I, myself, went from a Noctua U12S to a Cryorig R1 Ultimate air cooler which performs only slightly worse than the D15, but I prefer it's looks more. Anyway, my 5930K@4.2GHz with 1.17V is ~70Cs. Just jumping to 4.3GHz, it requires 1.26V and temps raises to low 90Cs. I tried 4.4GHz@1.32V for a split sec and almost hit 100C. I am staying at 4.2GHz because the jump beyond gets crazy hot. Really, if you want to hit 4.4-4.5GHz, you are going to need a very good custom water setup.
I've got a 420mm radiator with three Noctua PWM 1300RPM fans and my 4820k is getting up to high 70s low 80s package, high 60s low 70s core set to 4.4@1.275V depending on ambient. Should probably have gone with higher speed fans as I can't even hear them at full speed over the 295X2 fan at idle (which is still pretty quiet). I've got them spinning 350RPM at idle and my cores are 1-5C over ambient. That makes me happy. Not sure if package temps significantly higher than the core temps is a good thing, but it is what it is.
But yes, heat grows exponentially after a certain point, and stopping right before the neck is usually the best idea.