I have a journey using an APIEvent as the entry source. I have created a new version within the same journey but with a new APIEvent. Can both versions run concurrently with the different entry sources?
You would have to create them as two separate journeys for that to happen. As soon as you activate the new version, the previous one stops admitting new contacts. It lets contacts inside the journey finish it, but it doesn’t let any new ones in.
After a version is activated, it becomes the current version. New contacts aren’t admitted into previous versions.