Act 1? Is that the full campaign or just the first book?
Viewing post in No Room for a Wallflower: Act 1 comments
As spoiler free as I can make it, Act 1 is it's own campaign with begining middle and end that will take you from LL0-5. Act 2 instead of taking the ending of act 1 goes down another path to continue the story.
You don't need to own both to get a complete product or campaign, they just connect to one another.