OK, so thinking about this last night, I realized something. I had overlooked the fact that this is your first layout. I'm afraid I may be setting you up for failure in several aspects.
1) The transition between the levels will be tough, as will be figuring out how to support the upper level. To be honest, I don't know how I'd even suggest doing that.
2) The bottom segment, while gorgeous, will be very boring, operational speaking. If you just want to run trains through pretty scenery, great, but will you get tired of that?
3) As a first layout, that would be very ambitious.
Given all of that, I came up with another option. Build this single level version first. If you did it carefully, you could design it so that it could be modified later if you decided to build the two level one. But this would get you started with a layout that is interesting and fun. Best of all, the way I've drawn this, it can all be built on a single level, in fact you could just lay down plywood and build. This would get you started quickly, and allow you to see what you want. Then, as your skill improves and you decide what's important, you can modify it by elevating the "high line" or otherwise modifying it as you see fit.
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