As far as I’m aware the only information Twitch has released was back in 2017, with this Engineering blog post:
Live Video Transmuxing/Transcoding: FFmpeg vs TwitchTranscoder
Part 1 - https://blog.twitch.tv/en/2017/10/10/live-video-transmuxing-transcoding-f-fmpeg-vs-twitch-transcoder-part-i-489c1c125f28/
Part 2 - https://blog.twitch.tv/en/2017/10/23/live-video-transmuxing-transcoding-f-fmpeg-vs-twitch-transcoder-part-ii-4973f475f8a3/
Other than those engineering blog posts, Twitch doesn’t disclose the majority of their internal workings.