Someone suggested I should use
bcdedit /deletevalue useplatformclock
Reasoning that if you set it as bcdedit /set useplatformclock yes that breaks things and by deleting that value the system is free to use either clock.
After doing that and checking in windows I can see my DPC latency is as low as with bcdedit /set useplatformclock no if not a litte bit better.
So I'm set and finally the mystery is over.
PC Specs: 3900X - X470 Taichi - TridentZ Neo CJR 64GB 3733Mhz tight timings / 1080ti waterforce xtreme - H115i Pro with 4 fans + Lapped IHS + Liquid Metal.
Per CCX OC Settings: 4.5/4.4/4.375/4.375 at 1.331V (1.306V vdroop) Max AIDA64AVX temp 80c balanced AIO (23 room temp)