Aaaaaallllrrrriiight I am BACK with an update.
Enabling iommu=pt, cinebench R15 + R20 score remained the same.
This is also the case when removing manual OC + nohz_full and rcu_nocbs.
BUT! By disabling AMD Cool&Quiet on top of all above. Which seemingly shot up cinebench R15 single thread score up to 160.
I am not qualified what Cool&Quiet does, other then what the word say haha! But I do know that in Linux(GNU-Linux 
) you can change CPU governor, but when Cool&Quiet is disabled you cannot.
How can one option in the bios cause such deficit? I think leaving the clock handeling to CPU will allow for higher clocks? But the clocks stay stuck at 4 Ghz regardless of Cool&Quiet on or off.
Weird, but also interesting!
Before I enable back my old settings, I’ll use host-passthrough just for sanity check.
Update on that test: no change.
I’ll set this comment as solution. However there could be more in depth testing on each change. For now my recommendation is to disable Cool&Quiet for AMD cpu’s if you do vfio passthrough.