I don't know if this is of interest, but I just updated my i7-7800K on AORUS GAMING 7 to an i9-9900K and thought I'd share my experience.
BIOS update went smoothly, but did trigger the TPM so I needed the Bitlocker recovery password. I'd disable BL first next time.
I forgot to default BIOS settings after changing the CPU which caused W10 a few issues - so it's important to do this before first Windows boot.
OK, on to the real issue.
With stock CPU settings, attempting to run Intel XTU Benchmark or Passmark CPU Benchmark caused the VRM to hit current limit (you can hear the pulse inhibits in the coils) and after ~1s the MOBO reset.
To cut a long story short, I settled on the following fix: Set the P1(short term) and P2(long term) power limits to 135W. This significantly throttles benchmarks, but has no discernible effect on high CPU demand programs I run - specifically SIMULINK, PSIM (simulation), INVENTOR (3-D design) and QUARTUS (FPGA synthesis). When I time them, they follow the core MHz exactly.
I ended up with all cores at Turbo Clocks of 5.2 GHz, Vcore at +0.04 (dynamic VCORE) and have complete stability. When I benchmark/stress test, I see the throttling, and my VRM gets uncomfortably hot, but in normal operation this is a high performance and robust machine.
I know it's anathema to overclockers, but in this case I think Power Limit Throttling is my friend !
SUMMARY: This MOBO isn't well suited to the i9-9900K, but it can be made to work OK.
I'm off to explain to my wife why we absolutely need an upgrade to Z390 AORUS MASTER - even if we need to buy yet another Windows license......