A few suggestions, but nothing earht shattering, and caveat is that I have intel/nvidia set up, so not familiar with AMD world.
Check the RAM speed in task manager/system monitor - you need to enable the XMP profile in your bios to unlock the full 3200MHz speed. That should be easy and it should work, but RAM sticks that are not a pair may not work. Check that 3200 is shown here:
The screenshot you showed above that showed 1066MHz looks like the XMP profile is not enable or is not working. I suspect this is the most likely issue.
Chexk that your CPU is not power limited in windows power options. In power settings, go to additional power settings, then whichever plan you have, click change plan settings/change advanced power settings and check the maximum processor state is set to 100%:
In graphics performance settings, check that MSFS is set to use High Performance:
In the sim settings, clear and disable manual cache. The turn off multiplayer and turn on real time traffic. Then set the graphics level to low. With these settings you should be getting very good performance. If not, then there is something configured wrongly with your set up rather than the sim itself.
Hope this helps - I think it’s your RAM speed though