Windows power plan have a limited influence on ur cpu, foxus on checking bios settings first. Load default setting in bios and make sure you have newest version (F4 I think in case of ur motherboard). Instead of assuming auto did everything good double check eist, c-state and other cpu numbing stuff in on and cpu ratio is not set to fixed. If nothing helps you might just have something running in the background that's eating up ur cpu, keep in mind that even 10%-11% load will likely trigger turbo boost.
I Read you, done most of that, doesn't seem to be the issue here as a matter of a fact I am now not even sure there is an issue to be honest, by looking at HWiNFO the CPU Package Power goes as low as 4.308W and at the same time in task manager with zero % load clock speed stays well above 4.10Ghz.
Its kind of cool how this new technology CPU operates.