One of the bigger challenges I've had working with the ATEM Mini Pro was a clean audio workflow. When first plugging in, I found the audio to be clipping really easily with a really small window of acceptable audio and either alltooquiet or alltooloud audio. After playing with settings for a while, I think I've found the settings I like.

This video outlines a fairly versatile workflow that scales easily from one mic to six. Just as important as scalability is audio quality. I feel like this is the best audio I can get out of the device without upgrading our hardware considerably. All of the audio you're hearing is exactly as it was recorded on the ATEM with no compression, limiting or normalizing done in post. What you hear is what we taped (WYHIWWT).

There's a lot of gear used in this video.

A Camera Blackmagic Pocket Cinema Camera 6K with Sigma 1835 Art Lens.
BCamera GoPro Hero 3
Switcher ATEM Mini Pro
Audio Mixer Zoom H6
Monitor Atomos Ninja

If you have any questions about ATEM Mini Pro workflow, please drop them in the comments. Cheers!