Ryzen 5900X strange CPU Usage, low FPS

Your problem is different than this thread is about. The OP is not suffering from that RdrThread issue.

You might want to chime in in this thread, same behavior:

Also check your graphics driver settings (reset them to defaults), maybe uninstall it and make a clean install of the most recent driver. Check if you are running the most recent BIOS for your board and your chipset drivers are up to date.