So unless something has changed, it should turbo at 5.3Ghz when there are 4 or less cores being used. If all cores are being loaded, then it will drop to 5.2Ghz.
But Windows tries to balance the load across all cores so unless you manually set the affinity of the program you are running to only be able to use the first 4 cores, then it will most likely drop down to 5.2Ghz (the all-core turbo setting).
Sounds like a troll post since you didn't even give us any system specifications besides 'um, I have a 9900ks!"
That's not how per core overclocking works. Turbo boost ratios (# of cores loaded) is not per core overclocking. Turbo boost ratios set a turbo boost speed based on how many cores are loaded.
Per core overclocking (specifically--turbo per core limit control) only allows you to set the specific core that will run at the higher turbo boost ratios you specify, based on the cores loaded. You will *still* get the 8 core turbo boost ratio applied on all cores at a full 8 core load, and there's absolutely nothing you can do about that, no matter how angry you get. The most you can do is set which core will boost higher at lower core loads---IF the bios has the options for it.
What you want is to set a certain core or cores to be the physical core that turbo boosts to 5.3 ghz ratios, or whatever ratios you set, for the number of loaded cores. If your BIOS doesn't have per core limit control, you can't do it. Period. This option, *IF* it's in your bios, only works in combination with turbo boost ratios.
If the option is in your BIOS, but hidden from you, it may work still after you unhide the option. There is absolutely NO way to set an independent fixed multiplier for an independent core to have them all running at different speeds at the same time at full load. I am not even sure if HEDT allows such a thing on the X299 boards.
Maybe ask Win-raid to unlock this bios setting for you, if it's in the AMI UEFI capsule, that is.
You will need to get an IFR dump of your BIOS if amibcp 5.02.0031 won't open the menus without crashing. You can use CSME and run FPTW64 -d bios.bin -BIOS to create the capsule you need for dumping and future editing.
Note that only HEDT allows you to set a voltage per core for per core overclocking.
You can start by telling us what motherboard you have.