some thoughts based on a couple of preview days.
Mine cart appears to have the worse ratio of demand to capacity. I did not see a lot using a single rider queue causing it to be a walk on when I rode, but w/ four seats per vehicle, I'm not sure of a big need to fill seats via a single rider method.
When Monster's has a lot of vehicles running, it is a people eater. I saw very few using single rider and it appeared single rider was a walk on anytime I rode.
IF MoM has a single rider queue, I would think it a good option due to how many folks each ride vehicle holds, but this is a total guess on my part.
Stardust can be a people eater, but I often saw it running at lower capacity (even with both tracks open) than it is capable of.