Co-op Campaign Questions

So, I have a big question about co-op campaign mode. Mainly, if two people at different places in the game start a campaign together, how does that work. Does it mess with the one person’s progress to be at a different place than the other? If we have expanded to different locations, how is that handled. Will we resume our solo campaigns to find we have new festival expansions that we didn’t earn just by virtue of being in the same campaign with someone else who did? If a festival expansion is earned, do both players get to expand their solo festival as they see fit? Or does only the host player get the benefit of progress carrying over to their solo campaign, and the other three players are simply along for the ride the the leader’s festival? The game is a little vague on this.