Hi Rachel,
I would recommend checking out the documentation below:
A/B testing
That said to your questions:
1) Depending on how your workflow is configured and any schedulers or approvals in place when the delivery is sent out.
2) The winning delivery is selected by the Method in your screenshot. In this case open rate. So the winning delivery will then be used as the final delivery. What information are you looking to add?
3) Again it depends on if there are any approvals. Typically yes the delivery will be sent out automatically though.