Just get flex track. You'll save $. use it for the whole layout. Buy one piece of sectional curve for each radius to set up a jig. Watch the video on the GG site. Around the perimeter sounds good. You can always expand with a peninsula into the center.
there's a lot of great elements you can include. You can get maps and photos to help with your layout design. You have made it easier choosing a specific rr and a specific area to design your track plan. You'll just bend Kansas around for continuous running.
Here's a photo of Argentine diesel from the '60's.
