The only reason I would play with story progression off is if you wanted to make sure the other families that you don't control don't change while you play. I do this in order to control an entire neighborhood, but most people don't play that way.
As for LN to be for experienced players, I think that's really up to opinion. By all means, I would say dive into the new features, there's no better way to learn. And you can always read up about it on the guide first, find the answers to your questions on this forum.