i've found the issue. I have migrated the AMD system from Intel i9 Skylake-X X299 to Ryzen 5950 X570 without fresh install, i prepared and booted as it is on the new system and cleaned it up.
The Installed MSI Afterburner 4.6.3 Beta 2 lost its OC profile but it was still running in the background. After the migration ,the Afterburner failed to show the CPU cores corectly and i haven't seen all cores and possible parameter in the OSD config so i finally ignored the app for the moment because i was focused on the CPU OC. After i observed that the "freezers" have nothign to do with the CPU i did some investigation and tries, also with the help of this thread, finally nothing worked for me. The "Preferred Maximum Performance" mode of the graphcs card was the last try i did from this forum, what resulted in idle 80-100 watts more power consumption, less power boosting and finally even less points in "Unigine Super" Benchmark, same Points in "Unigine Heaven" and litle less performance in Valhalla and Serious Sam 4, but still - surface freezeres and a fully operable system via RDP. After some more observations i checked what else can affect power management and got the idea with MSI Afterburner which is even not workig correctly. I removed is and the RivaTuner app and removed all settings, switched card back to normal operation mode. Within 2 days constant on (disabled S3) with hours of Valhalla gaming an idle, keeping Curve Optimiser UV and OC on as it is (i saw no relation between OC and these freezers - they were always the same - too constant for OC related issues) the PC run well without any Error 14 freezes anymore and very stable, hours longm gamung fun, so also no freezes in game menu). On 30.12.2020 a new version of MSI Afterburner has been released on Guru3d, 4.6.3. Beta 4. I have reinstalled it and i was able to configure all cores correctly, i did also a Curve with the Scanner and saved it, someting what i havent't yet made on the Ryzen system. I have still no Error 14 / surface-freezes anymore. Right now i can say that the issue came from MSI Afterburner after the migration, was fixed removing it. If the reinstallation of same version would also help or bring the issue back i can't say, i tried newest verssion 4.6.3. Beta 4 and this results in stable system with same OC Curve on 3090 as on the previos Skylake-X platform.
If you migrate withot a fresh reinstall, observe MSI Afterburner, it can cause such issues. This system here has been multiple times migrated from Vista to Windows 8 to 8.1, from MBR to GPT/UEFI, to Windows 10 through multuiple Hardware releases and now finally to AMD x570 / Ryzen, there was no fresh insall since 2009.
i just like to confirm the finding an solution