I have done some testing with the PD capture function.
What I see is the settings are far from user friendly: The PD capture settings apparently needs to be done in the right order, because after setting the camera resolution and/or the microphone volume, the output file format is set back to the (low) default. So, if you use the PD capture, set the volume first, then the camera to (probably) the highest possible (the default here is 640:480 too), and then set the output file format. The saving of the file format is not easy and is also reset to the default after the camera or microphone settings.
Although you record with 16x9, your resolution is 640:480 which is an aspect ratio of 4:3. I would guess that your webcam at least can be set to a 16x9 ratio?
Furthermore, some testing proves to me the PD capture is apparently not able to cope with recording of video and audio at the same time and keep both in sync. At least that is what my testing shows even on my very fast state-of-the-art laptop.
So I have the same findings as you: The sound is jumpy and choppy and then totally unrecognizable. The video is out of sync. This has likely nothing to do with your settings.
I have also tested a recording of video and sound using the
CL Screen capture software, that comes with 365. Here one also needs to carefully look at the settings, but it
gives far better results. Maybe that is a good option for you too?
With respect to running a test with a (photo) camera (or smart phone) as I suggested: these can give fairly good results and may the alternative to go for if the screen recorder does not work for you.
I am curious to see what the experiences are of other forum members.