I don't think there are any S&S areas inside of the Studios.
All I can think of is a "Party Zone" for Passholders which works the same way as a S&S area, but that will only be open on non-Peak nights (non-Fridays and Saturdays). Other than that, I don't think there are any Stay and scream areas inside of the Studios. But I can be wrong, as Bev said, we won't know the official S&S areas until the event happens.
As for the pathways, it sounds more confusing than it really is. It really is very straight foward. But, if you get confused, there are signs all over the park and the map should have it clearly drawn out.
As for Express Pass being for the 1st Bill and Ted show only (which, btw is in the Toon Lagoon amphitheatre) I don't think you'll have much trouble getting a seat for any showtime. The theatre holds quite a bit of people, and they have plenty of showtimes throughout the night. Express pass may give you a closer seat, but IMO all seats offer a good view, and that closer isn't always better, last year some action (and dancing) took place on the walkway seperating the two groups of seating (kind of disturbing having John Kerry dancing 2 feet away from you, directly in front of you, lol)
Most important, is to realize that when touring
HHN, or any theme park, you need to do things the way you want to do them. We've all posted our own opinions, but they may not be suited for you.
Here's is a
link to the official website, there may be answers to your questions here.