Start from the inspector, not a forum post
A common 1080p60 target people have used for years sits around 6000 kbps, with 720p60 lower. Enhanced broadcasting and higher resolutions change the ceiling, and Twitch’s own recommended settings are the ones that match your account. If you are dropping frames, lower the bitrate or the resolution until the line is flat.
Your upload should be comfortably above the bitrate, not equal to it. Other people in the house, a Discord call, and a browser source all spend the same pipe.