"Start livestreaming automatically": when this option is activated, there will be no videoconference, clicking on "start" will automatically launch the live.
"Start recording automatically": by checking this option, starting live will automatically start a video recording.
"Hide the overlay": by checking this option, the information at the bottom right of the video sources will be hidden for you and your speakers. Note that live viewers never see the overlay.
"Only the main speaker can share his screen": when this option is checked, like document sharing, the speakers will have to ask to be the main speaker to share their screen.
Layout: this option allows you to change the layout for screen sharing and document sharing. When you close the screen or document sharing, you will find the initial layout.