I did RnRC once as a single rider and it took quite a while. I don’t remember how long exactly. I do remember it took so long that they actually took people from the single rider line to fill at least one train. Not pulling one person at a time. But took 20-30 people straight from single rider.
Smugglers Run works well, but you will almost always be in the engineer seat. If you just want to ride though, it's finr. RnRC doesn't work well, and I think you're better off in the regular line to be honest.