These console commands doesn’t change the framerate during play :
-usefixedtimestep -FPS=60
Try play any project, show the FPS with ‘stat FPS’, you will see your FPS doesn’t change using these commands in the console.
I suggest you configure these values in Project Settings > Engine > General Settings > Framerate and set the fixed framerate you want to use
But if you don’t want to change your project values, you can set these values when you launch your game project for recording.
UE4Editor.exe Path/To/Your.uproject -game -usefixedtimestep -FPS=60 -notexturestreaming
This will start your game at a fixed FPS. That’s what I use for any video (panoramic or not) recording.