Did a test, turns out it is ridiculously easy to stream in Discord and would make it so anyone who wanted to could observe. For those interested:
- Open Discord on PC (phone version won't work)
- Open Among Us through Steam
- Minimize Among Us, pull up Discord
- Go to the server you want to Stream in (so the SWCCG one)
- In the bottom left corner right above your username you'll see a Go Live button, click it
- It'll ask you which voice chat you want to stream in, pick the Among Us one
- BAM. You are now streaming in Discord.
There may be special permissions needed to stream in the server, and without Discord "Nitro" you can only stream at 720p, but for the purpose of observing it would work pretty well. Obviously other people in the game would not be allowed to watch the stream or they'd know the role of the streamer. I am 99% sure you can join the voice channel without watching the stream though so it shouldn't be an issue.