Pro Hobby. To answer your question and keep it simple, is yes. 3RS implies that your cars are prototype and to 1/48 scale. Kadees yes. 2R wheel sets optional providing that your track will support them.
So, is converting to Kadees .... pretty much .... a hallmark of 3RS? Prototypically correct equipment (scale, era, and locale) with Kadees?
I ask because all the rest seems so subjective to me, such as how much scenery detail.
I don't know. I don't even think I understand what hi-rail is. lol