I have followed all the instructions (I believe) but if I can see my webcam whilst I record the screen (which I am also recording) then when I view the final video I see the webcam twice - the one that was recorded (which is rectangular) and the one I could see on the screen during the recording (which is square in shape). If I enable the Preview option, the second (square) webcam view only appears when I saw it during the recording (i.e. as I toggle the Tab key).
I have a Microsoft surfacebook, I am recording the main screen, but I do have three monitors connected. The webcam is the surfacebook's webcam. I am recording the entire screen. I have attached a screenshot I created when testing.
As a matter of interest, is there a way that I can turn off the webcam whilst recording - so people don't see my face and will focus on the screen - sometimes the webcam will be covering something important on the screen regardless of where I position it.