To address your question about O Gauge, it's tough to beat Lionel tubular sectional track, or even its equivalent from Menards. You have a lot more choices with O Gauge than standard gauge, especially for switches. If you're running tinplate, try to find the K Line Super Snap or O Line Reproductions switches. Just about everything, from the oldest tinplate to modern trains, will run right through them, even the prewar wheels with deep flanges.
John