The "SWB Audio Capture" section is all about monitoring the audio driver.
If you see a level meter bouncing here; you've got audio coming into the driver. This is a good thing :).
Want to know more about how the SWB Audio Capture driver works? see: https://youtu.be/CQUTadBGnDA
Make SWB Audio Capture default output
What this does is when you enable preview, sets the SWB Audio Capture driver to be the default output device for audio. It's useful if you've an app you want to capture; that doesn't let you specify a specific device to output to (so you can't change it to output directly to SWB Audio Capture)
I saves you having to go into System Preferences | Sound | Output, to change the default output device to be SWB Audio Capture any time you want to capture all audio from macOS.
Instead; when you enable preview (see Complete SWB Audio App: Previewing Audio), the driver is made the default output device, and audio is routed to the preview target.
When to use it?
When to use:
- When the app your capturing cannot output directly to a specified device (so you have no choice; if you want that apps audio, then you must make SWB Audio Capture the default device).
- You want to do the above; and preview the audio in one click. It's a convenience :)
When you don't need to use it:
- When the app / capture setup your capturing:
- can choose to output audio to a specific device
- you have alternate monitoring capability. e.g: OBS.
In the above case; an app (like GarageBand) might be outputting audio directly to SWB Audio Capture.
You would then setup OBS to monitor that audio input, to whatever monitoring device you like. This is exactly the same as what's being done by SWB Audio App - just it's being done by OBS.
The advantage would be if you are managing many other video / audio sources; that they are managed by one app (in my example, OBS). Other than that it really is a matter of personal choice.