Happen to think that in my above pic I snapped a few years ago of an S scale figure compared to an O scale figure, I didn't allow for the large flanges that 3-rail uses. SO, I made another pose, this time using something to raise the figures up about even with the tire of the wheel. That way, the large flange isn't part of the equation, thus not exaggerating the height of the engine. (Besides, most service areas have/had concrete or dirt/gravel/cinders and the ball of the rail is even with the concrete or dirt/gravel/cinders.)
Yes, that figure on the right was sold by one of the 3-rail mfg'ers as "O scale/gauge". I can't recall the name of the mfg'er, though. However, it's not as oversized/ill-proportioned as the "Homie" series of figures. (Which I would avoid like the plague.)
Again, for me the choice is obvious.
Having said that, I suspect there would likely be issues using S scale figures/vehicles with structures that are true O scale when it comes to the doorways. That tendency will be made worse if the structure has oversized doors, which I feel is the case of the structure in this comparative photo:
(FWIW: The above gigantic so-called "O" gauge/scale figure hits his head on the top of the door jam when placed in front of the door!)
Interestingly, the above structure is nicely "compressed" in every way but the doors, which are, to me, oversized.
Anyway, this 1/43 vs 1/48 vs Options can truly be a rabbit hole.
As stated, given my interest in 3-rail would be focused on traditional-sized trains, S scale figures/vehicles look best to my eyes among the smaller traditional-sized equipment.
Oh, and yes, should I ever go to 3-rail, in view of my visual goals for such a layout, my choices for suitable equipment would exclude Lionel's PW offerings such as their GP7, NW2, Train Master, etc. True O scale models look way oversized compared to the Baby Hudsons, PW-type FA's, 6464-type boxcars (which would be the largest boxcars I would use), along with other similar sized pieces of traditional rolling stock.
HOWEVER... in spite of the rabbit holes to avoid, I think if I exercised discipline with my equipment and structure choices, and used S scale figures and vehicles, I think the end result would be a layout with a visual impact that I would find pleasing.
I was headed in the right direction back in the early 2000's with my compact "KC Lines" layout idea... but I derailed myself by migrating toward Hi-Rail w/scale sized equipment. Silly me.
Case in point: Overlooking the scale boxcar in this pic (and the Railking NW2 is a bit too big)... the rest of it was headed the right way...
Sheesh. The above is a lot of drivel for a conversation about 1/43 vs 1/48 vs Options. What a putz I can be.
Andre