First I want to say thank you for all the extensive testing. It’s very insightful for us who are trying to determine our next CPU upgrade. I would support your belief you are GPU limited as that’s what 4K does, puts the strain on the GPU, not the CPU. I suspect it’s why you aren’t seeing that much of different results in your Vcore vs. non-Vcore results. The only CPU thing you can somewhat suss out is 1% and 0.1% lows when doing a 4k test.
If you really want to test the CPU you need to make sure you aren’t GPU limited by running your tests in 1080p. Sure it’s not a test which is realistic as in you won’t want to game with that resolution, however it will answer your question on what is going on with your CPU.