I need to comment. The orginal post assumes that the 27 books were widely accepted in the second century. BIG FALSEHOOD!
Most of the 27 books were not even known!
The earliest gospel (out of the four) we have evidence for is a piece of John and it is around 125 or so. (could be earlier but not much)
The earliest NT canon did contain a gospel. 'The Gospel of the Lord'. It was a proto-Luke... meaning is predated Luke... when was this? 140....
Also in that concon were 10 so called letters of Paul (Ephesians originally was called ''To the Laodacians' and all of the 'Pauline letters' are proto-letters. Very gnostic. (The Pastorials we have no evidence for until tha very late second century.)
The have no evidence for Matthew Mark or Luke until the mid second century. (Later for Luke) and the referances in Mark 13, Matthew 24, Luke 21 all refer not to 70ce but to the Jewsish revolt in 136ce.
The Didache was originally dated to the early second century and if so that text plus the Gospel to the Hebrews made up some of the material unique to Matthew (As well as oral traditions)
The only exception I could make to this is Revelation. Parts of it are clearly first century but this is one of the most edited books in the NT.