If you haven't purchased track yet, you might consider Fox Valley track. They have turnouts for scale wheels. It is a lower profile track than the AM track. Code 138 I believe. There is also a mod you can make to the Fox Valley hirail turnouts so they can run scale wheels. It can be found on the forum. S is one of those scales with too many variations to consider. The nice thing about HO, pretty much everything runs anywhere apart from radius constraints. S is still the perfect size, though.
Brendan