I have finished reviewing the Tiefling stuff. If people want to use the Tiefling variants, they have to roll randomly to see which one they get. They also have the option to roll on the random feature table. There is a feat available to give you more control over choosing your variant and random feature.
I would also like to note that people in Cheliax (and hence Westcrown) really hate tieflings. Really hate tieflings. One would think that an evil society that worships Asmodeus would be more tolerant of them, but Chelian society is an orderly premised on summoning, binding, and controlling devils. Tieflings represent a loss of that control, and that is unacceptable to many people. Tiefling characters should expect to get a lot of shit from people.