Full details can be found here https://wiki.batc.org.uk/Configuring_ATEM_Control
Please report any bugs here.
I'm currently converting my own repeater control to the ATEM.
However, I use compenion for this.
First of all, you can set up the ATEM using Blackmagic's control software.
You can assign both HDMI outputs.
So you can switch both outputs to the MultiSource.
You can import various multisource templates and then save them in the setup. This setup will be loaded again when you switch on.
You can switch the audio inputs (including the analog ones) on and off.
With compenion you can change a lot of settings.
You can easily trigger/switch this on/off from a control program using webhooks.
This is only a small part of the possibilities.