Can you hear random popping, no matter which mic is used, built-in or usb, from your ManyCam recordings? As do I.
Tried to use a separate mic, independent of the computer to better audio? So did I.
I record my lessons and usb mic during the online session, yet because of the constant popping, I’ve decided to use a separate mic on my 2nd DSLR, which is exactly sync with the video. Much to my chagrin, when I upload the .mp4 to Final Cut on my iMac, the video recorded by ManyCam is slightly faster.
Slow down the .mp4 file by 4% - set at 96% - in Final Cut and the audio from your separate mic source should sync close enough to be barely noticeable.