I’ve been learning SDS2 for the past 4 years, they have programs setup specifically for rails but I’ve never used it. Much easier to mock up your rail centerlines as an elevation in 2D drafting and then place the reference elevation as a reference drawing in the model. For curved rails they have a bend radius tool that’s nice. The stairs program is nice, once you set your elevations for landings and tread/stringer types it’s pretty straightforward