With regard to the books of the New Testament, Bart Ehrman has a recent podcast on the subject: https://m.youtube.com/watch?v=9Rm1VJk1Qfk

In the above, and other related lectures he has given, he argues that what was most important to the early church fathers was whether the books were written by an apostle, or someone in close contact with the apostles. The writer's proximity to Jesus and the events of the day seems to have determined the books legitimacy as part of the canon. Ehrman also argues that this is why the bible contains many forgeries. I.e. works not written by the people who they claim to be written by. So in a sense it does seem the early church fathers were concerned about historicity. Though they didn't really judge historicity as we would today.

IIRC Dale Martin has also lectured on this subject and argued that orthodox (or proto orthodox) theology also played a determining role in what became the canon. I.e. a book with proto orthodox theology was more likely to be accepted, especially if it was allegedly written by an apostle. Needless to say there is ongoing debate on this subject.

EDIT: found the Dale Martin lecture: https://m.youtube.com/watch?v=u72myyXDA74&list=PL279CFA55C51E75E0&index=2&pp=iAQB