Compass fallback testing

With regards to GPS for Yaw.

I’am about to make a test using a GPS for Yaw setup based on two zed F9P modules.
What I want to test Is a copter behavior when it does compass fallback. First question is - do You have any way to do that other then mechanically lets say disconnecting one of the GPS modules?

I tough it would be a good way to do it like it is written in GPS-NONGPS transitions. GPS / Non-GPS Transitions — Copter documentation

So to setup all EK3_SRC the same except for the Yaw source which will be 1: GPS, 2: Compass 3: GSF

And with regards to that setup.
1: Would changing source from 1 to 2 by switch be equivalent of the function that is implemented in GPS with Compass fallback?
2: EK3_SRC_Options - as those are velocities fusion would it be okay to live it on 1 ? or should I go with 0? If someone could point me to what this parameter exactly does?

Thanks in advance!