Matt, wow! 200 degrees is way over the top. I wonder if something else is amiss there.
Just thinking out loud...... because that just doesn't seem right at all. As always, YMMV!

I've "rolled my own" Windows PC's for many, many years also, and never encountered temps that high.
My mobo, Corsair liquid cooler, and Corsair power supply are constantly monitoring voltages and temps with an app from Corsair, auto alarms if anything goes out of spec. Been running this rig for 3 years, mostly always on, through all the variations of Windows 10 to the current 1809.

Power Management is always on High Performance, 100% on Minimum and Maximum, Active management. Temps on the actual i7-6700K CPU cores have never gone above 95F, and the water cooler temps have always been right around 85F.

In my case, I've seen plenty of weird settings get changed through Win10 updates, but I just haven't seen anything in my Power Management ever change.
I can only hazard a guess, remotely here, but I'd at least consider that "something" mechanical / thermal paste / air flow could be the culprit.
You really "should" be able to run at 100%. My .02 !


Jerry
2019 BiaB Megapack (634), RB 2019 (Build 4)
Reaper 5.983 x64, Audient id14 USB interface, Voicemeeter Potato 3.0.0.8, Nektar LX49+, Roland E20
i7-6700K Skylake desktop, 64bit Win10 Pro(1903), 32GB ram, 512GB system SSD + 2TB data SSD