Are the AF and S-Helper all pretty week scale or is the AF more toy-like high rail. I have zero knowledge here.
Here is a comparison of a Postwar Flyer boxcar with an SHS double sheathed boxcar:
It takes a little work to convert a Flyer car to scale, but it does add a little variety. Here's some conversions I did way back in the 80's when I entered S. I'll admit nowadays I probably wouldn't bother converting Traditional Postwar-Style Flyer to scale:
Are they perfect? No, but once the 5 foot rule is activated, they fit in just fine.