Quality testing audio compression / Separating the video quality settings from audio quality settings
You could consider separating the video quality settings from audio quality settings, since audio quality is far more important than video for some content.
There are Music and Performance streams and such where we're interested in listening to the sound more that looking at text / faces / fine details.
New show hosts frequently receive advice to invest in buying better audio equipment to improve audio quality before looking to buy more expensive cameras. This is because people will tolerate bad video in a show much more than bad audio (although 160p is still kinda bad).
I've listened to several streams where notes seem out of pitch and the stream chat/host think it's probably compression. It seems to be worse at 360p or 480p quality than at higher.
You might just want to do another round of quality testing on the audio compression.
(I'm not actually sure whether audio is actually compressed any further/differently at different quality levels but it seems to be.) The problem might be when broadcasting audio that has already been compressed, like by apple music or youtube?
Some streams you could mute and watch at high quality, other streams you could play in a secondary browser tab and presumably not require data for video that you're not watching, and I think the chat window might pop-out somewhere if you just wanted to follow that without watching the show, but there might be a problem with trying to listen to high-fidelity/quality audio without stuttering.
because when you switch tab, the quality gets reduced by twitch to 480p oder 360p where you can notice a significant audio quality drop. would be nice if they could add a feature where they disable the video feed, when not in tab, and re-enable it when you come back. or as you said, disconnect the audio quality beeing adjusted to the video quality (for example: 1080p 320kbit, 720p 192kbit, 480p 128kbit, 360p 96kbit)
it would be great if you can add a thing where you can mute for example the game sounds, streamer's mic, music that is playing so u can play your own music.
Currently people are stuck watching streamers that play music the viewers don't like or listening to game audio that might clash with their own. My suggestion is to split the single output audio channel into multiple audio channels, which would directly also require software updates on not only Twitch, but also the streaming softwares.
Streamers can still play the music they want, if viewers don't like it, they can turn it off and play their own music.
In addition it will make vods more watchable as well, since copyrighted music streams can be turned off, without muting the entire stream sound.