Webinar: Speaker vs Panelist

As above what is the difference in those roles in ZOOM webinar. As Panelists I put all important people that will contribute to the discussion. I am a host and opening event with housekeeping rules and after wont participate at all. As speakers I should put all panelists and myself? And for visual part: If I am putting Speaker mood, attendess can see only the person speaking now, then if I will swich to the gallery who can they see, hosts (?) just the people with camera on (?), all assigned as Speaker role (?)