Becky - you can set up the meeting to include a Q&A and a Chat session... When we've run Live Events we usually have a Q&A so that the presenters can accept questions, answer them privately, speak to the answers, or answer them in writing and publish the results to all attendees. If we have a Chat session we usually announce that it is unmoderated and the presenters won't be following it, so it's solely for interaction between attendees... but if you have a big enough presenter/producer team you might be able to have someone participate in the chat.
Participation in the meeting can be limited to people within your organization, and the attendee report you download after the meeting shows when they each joined and when they left the meeting... but in our last event there are about 16 'join' events out of close to 700 that don't have names... which might mean we didn't correctly limit participation.
I don't know how to poll the audience during the meeting - I'll let one of the experts answer, but I suspect there's a way to do this with a Yammer poll inside the event... but I don't know how to make that a seamless experience for the attendees.
RG_IITM - for a Live Event, unlike a Teams Meeting, the Producer controls exactly what the audience sees - so it's very easy to pin the organizer's camera feed or screen share so that nobody will see anything else.