Hi Andy,
There almost always going to be a small video delay when going through data switching due to video processing, which is separate from audio.
As a rule of thumb, you can estimate 1 frame (33ms) of delay per switcher. (Barco Image pro, etc). You can delay the sound with most digital mixers, or get a delay unit in line for analog mixers. You don’t want to delay too much since that will affect the person on stage when they hear their own voice delayed in the PA.
If you are only worried about recording and not iMag, delay away!
Vince Becquiot
Indigo Live | Kaptis Media
San Francisco Bay Area