How the fuck an RPG can be on Early Access?
They say they are gonna explain their early access content and philosophy at the live show, but it will probably work similar to Larian's previous game, Divinity Original Sin 2.
That game started you in a huge playable area that was a Prison Island called "Fort Joy." There was a ton of content there that took around 15-20 hours by some estimates but it was also very replayable with different classes to try or variations in quests.
Once you finish Fort Joy after a large boss battle you set sail off the island and begin Act 2. So all of Act 1 on Fort Joy was the early access portion of Divinity 2.
I don't think people were able to carry their save file over from Early Access to the retail release of that game, but I may be mistaken.