The message on the screenshot of the OBS Settings says:
"
Twitch Enhanced Broadcasting is controlling some of your stream settings" (in case it cannot be read by screenreaders or seen in other way).
that means that you have enabled special mode of streaming to Twitch,
thus some settings were disabled.
It is poorly documented in OBS ( here is what "info" will be shared with the service:
https://obsproject.com/forum/threads/obs-studio-30-2-rc.176114/ ) and in Twitch itself ( basic info:
https://help.twitch.tv/s/article/multiple-encodes?language=en_US and few general words in
https://blog.twitch.tv/en/2024/01/08/introducing-the-enhanced-broadcasting-beta/ ).
In short - the "Twitch Enhanced Broadcasting" is transfer, from you to Twitch's servers, not just 1 but 4-5 streams of the same content but at different resolutions and frame rates (for example: 1920x1080@60 6000 Kbps + 1280x720@60 2500 Kbps + 820x480@30 1000 Kbps + 640x360@30 500 Kbps + 284x160@30 200 Kbps, in total = 6000+2500+1000+500+200 = 10200 Kbps instead of 6000 Kbps with regular broadcast). This requires 4 additional encoders running on your PC. Same task but when it running on server's side of the online service is named "transcoding". For example, YouTube do it for free, Twitch - for money. For compatibility and performance reasons most of the parameters for "Enhanced Broadcasting" cannot be adjusted by user. Thus, you either using "Enhanced" broadcasting (and controls almost nothing) or using regular one (but still should fit all your settings to requirements of the service).
Some feedback about the feature, here, on the forum:
https://obsproject.com/forum/threads/possible-to-tweak-enhanced-broadcasting.178887/
To disable "Enhanced Broadcasting" go to main menu
File > Settings > Stream and make unchecked the
Enable Enhanced Broadcasting setting (the option available for
Service = "Twitch")