Your plan is similar to what I did but 6x16. I have less sidings but two loops. I violated all the rules of model railroading. It's an island broke rule one. Modeled the flatlands oops. Last but not least I have two parallel mainlines around the perimeter. The proverbial race track, oh well. I'll try and post a picture later. Depends what you want to do and how realistic you want to be. I am more Flyer but run AM, SHS and Lionel Flyer probably more than my Flyer.
I also used AM track a mix of the R27 curves, straight sections and flex. The complaint is their track is brass rather than nickel silver but I'm pleased and so are others.
Rusty is right the turnouts need to be modified for scale wheels. I'm a fan of high rail wheels even if everything else is scale. That way if you find a Lionel or MTH you got to have you can run it without major modifications.
I'll leave tweaking track plans to the experts. I do like my AM DL&W Train Master.