Which JSON-LD Schema types for Event & Video Google enhancements should I use for future video broadcast events?

Question

I'm working to publish the meta information for a SaaS platform emitting live events, video broadcasts live shopping sessions.

In order to take advantage of Google search enhancements for each upcoming event, I selected the schema object Event and generate the JSON-D info on the page. However, when the event starts, technically it becomes a video stream, and as I understand from the google dev docs, in order to be eligible for display with a LIVE badge I think I need to expose the JSON-D info as a VideoObject with the selected BroadcastEvent properties nested (publication.startDate, publication.endDate, publication.isLiveBroadcast).

I'm trying these approaches:

1. Published as Event, turning into Video with nested BroadcastEvent properties once started live.
2. Published as a BroadcastEvent all the time. publication.isLiveBroadcast change to true once started.
3. Published as BroadcastEvent, then turning into Video with nested BroadcastEvent properties once started.

Option 2 seems the better choice to me, the only problem I have with the BroadcastEvent object is a property named broadcastOfEvent, because I'm not sure if it can be null (which will be my case if selected because this page is referring to the event that is a broadcast by itself).

In your experience, which of those metadata changes could be noticed fast enough by the crawling engine and what is the recommended way to go in this scenario?