Update: I connected to group chat for the first time today just now, and to my amazement whisper lag with my bot appears to be eliminated! In addition, group chat messages no longer appeared late as described in my earlier posts! I’ll keep you guys updated if this annoying lag comes back anytime soon. Thank you so much Twitch Staff, including you @xangold!
So to conclude this topic for the time being, what caused this kind of lag to appear? Nevermind, I guess the migration to AWS fixed it after all