Allow main stream to not stream and instead use the horizontal canvas

I want to record my main preview with no UI elements (no webcam, no chat overlay, etc). I want to then have my horizontal to stream to twitch and youtube, and my vertical to go to youtube shorts and tik tok. I don't understand why it uses the main preview for the main stream (twitch in my case), the horizontal canvas for youtube, and the vertical for tik tok and youtube shorts.