I decided on the option 4 track plan but I changed the inner oval to be raised versus the outer making the overpass a bit more complex. I made a “mockup” of the layout pinning the tracks to the foam board and created “elevated track support” out of cardboard. This is a great way to literally see the mechanics of the layout.
The gradient is steep but I am not so concerned about that. I can see how the raised curve may bank a bit and that can potentially be a real issue. The magnetic wheels will help in both cases though. I need a short straight track to connect the elevated curve with the 60mm straight track. Not ideal but I will try to hide that section.
I did also decided on the layout theme. I will build something ultra modern with a “sun powered tram” serving a multi story shopping/transport center. I will incorporate the tracks into the structure with 4 stops. Modern architecture with a lot of straight lines, rectangle and “squarish” elements looks like a perfect fit for 1/450 scale (or not).