In order to visualize how the Hybrid Stage works, you can think about a TV show with an onsite audience that is broadcasted to a wider online audience. In this context a panel discussion, or simply a panel, involves a group of max 4 people gathered to discuss a topic in front of an audience, typically at scientific, business, or academic conferences.
There are tho only 4 audio channels, which means only 4 people can be hooked on to a mic at the same time. Please consider this when planning the number of speakers and for example that you have 1 channel free for the audience mic for questions. Speakers on stage can of course share a handheld microphone.