Our layout was all Atlas solid nickel silver, and once I modified all the turnouts (by adding styrene shims to the tops of each guard rail, so as to be the same height as the running rail), I had no more trouble with 2-Rail SCALE freight rolling stock (even reverse moves through turnouts). All equipment was up-graded to body mount Kadee couplers.
Concerning the curves, pretty much everything on the main lines was larger than 072, up to 099.