Currently the various locations highlight some of the different modes / mechanics you'll see in gameplay. The Skyline / Sewers / Spider Caverns are all survival wave maps though currently, so those are pretty similar. Most of the actual game will be in mission format similar to the Slums.
The major difference with the subscription is the monthly progress update (usually a few pages long, showcasing progress on content that won't be seen in game for a while). On SubscribeStar we have a Discord tier, where we share a lot more updates, basically daily.