How does the platform work in regards to session interactivity? For example, can we have break-out groups in our session? Or digital mural interaction?

Each session has an assigned tech support that can help session participants to set up break-out groups.
Session organisers can self-organize interactive digital boards and share the link with participants during the meeting.

Can I have a shared board to collect ideas from my session?

You are welcome to organize a shared board. The session will run in Zoom. So there is no inherent platform to collect ideas. As a session host, you can however choose one of your liking (for example Miro.com or Mural.com) create the board before the session and share the link with your participants at the beginning of the session.