Excuse me.
I didn’t realize that the installation was completely clean.
We can see with the Simulator started in task manager how everything works…?
CPU
RAM
GPU
Also see the processes that may cause this stuttering.
Have you excluded the FlightSimulator.exe process from your antivirus?
And the folders related to Microsoft Flight Simulator.
In my case with Windows Defender I was able to remove my CPU spikes and possible causes of stutters.