A couple of friends do a 1-player (and 1 GM) game in the Chronicles of Darkness setting (https://en.wikipedia.org/wiki/World_of_Darkness https://en.wikipedia.or

A couple of friends do a 1-player (and 1 GM) game in the Chronicles of Darkness setting (https://en.wikipedia.org/wiki/World_of_Darkness https://en.wikipedia.org/wiki/World_of_Darkness). It focuses a lot on mystery and investigation so it seems to scale pretty well to differing group sizes. While I don't play in that game, I assume there is still much of the usual prep work done on the GM side so it may not quite fit what you're looking for.