I think what makes a good 1x1 is the ability to write a good selection of sub characters. They'll fit better into the world because it's your own world with only one other, as opposed to a group where you follow a certain lead... but that's a bit off topic, maybe... confused by the title and maybe setting should be swapped for "structure"

I usually prefer technology in my RPs and will do fantasy only if it's not too history or European based. Usually medium size groups with a slightly slower pace so that I can keep up.

I can elaborate more, just not sure what the topic is about since you mentioned that you don't wanna discuss stories and genre. xD