1. Matthew's Gospel
Was the Greek version of Matthew originally written in Hebrew? If so, what impact does this have on the canon? For more information, see The Original Matthew.
2. What Was Original NT Scripture?
Metzger is considered the foremost expert on canon formation. Listen to whether there was any self-awareness that letters prior to Jesus' words being written down were Scripture i.e., the period that Paul's letters were the only circulating written materials prior to 50 A.D:
"For early Jewish Christians the Bible consisted of the Old Testament and some Jewish apocryphal literature. Along with this written authority went traditions, chiefly oral, of sayings attributed to Jesus. On the other hand, authors who belonged to the 'Hellenistic Wing' of the Church refer more frequently to writings that later came to be included in the New Testament. At the same time, however, they very rarely regarded such documents as 'Scripture'.
"Furthermore, there was as yet no conception of the duty of exact quotation from books that were not yet in the full sense canonical. Consequently, it is sometimes exceedingly difficult to ascertain which New Testament books were known to early Christian writers; our evidence does not become clear until the end of second century." (Metzger, The Canon Of The New Testament: Its Origin, Significance & Development at 72-73.)
This is why the better answer is canon is the inspired words of the apostles when recollecting Jesus' words. For Jesus instructed them for 3 years. They were the only authors of true canon when recollecting Jesus' words. Interestingly, Greg, a highly conservative reformed writer, affirms this in 2015. At the same time, he tries to squeak in Paul, without telling you Paul never quotes Jesus in his epistles except  from the liturgry of communion and  one vision experience in 2 Cor. 12:7 that "my grace is sufficient for you" - Paul's Jesus denying Paul's request to be released from an "Angel of Satan."
As to the latter, most scholars believe this cannot be in the form Paul intended, for it means our Lord refused Paul release from a demonic spirit. Thus, Paul "has revelation" of nothing new that is not in the apostolic gospels or that carries a message for us from Jesus. Hence, by this correct criteria, Paul is excluded. Listen carefully:
The word "canon" means authority. That is, what are the authoritative works in themselves in the New Testament era that tell us about God and His plan for salvation? Before they were books for the New Testament, what was the canon?
Jesus trained 12 people (and more if you consider Paul after the cross) to take His message, and promised them in the upper room discourse in John 15 that He would bring to remembrance all the things that He had taught them so they would be able to communicate to others. Because of their close association with Jesus, this group of men became the standard, or the canon. (Greg Cohl, How Were The New Testament Books Compiled, July 14, 2015 at this link.)
Greg is 100% correct. Jesus said the 12 would recollect His words, and that is canon. Hence, you cannot squeeze Paul into this principle because Paul repeats nothing Jesus said except the liturgry which is lifted from Luke's gospel anyway.
3. What About Enoch?
This was part of the Hebrew Scriptures that Christians recognized from the time of Jude (60 AD) to 365 AD when it was dropped from canon. Might this have been wrongly dropped?