I would agree with the caveat that it was the Holy Spirit that was directing them. I believe this to be the case because if it were solely accomplished by the will of one like minded group in 1800 years we would have found books that clearly should have been included and books that should not have been included.
BTW, I do like your description of the early church. I think the different churches that left, or never became a part of the dominant church is a natural result of centralized authority.
“I would agree with the caveat that it was the Holy Spirit that was directing them.”
I don’t doubt for a minute that the original “source” of the necessary “knowledge” to determine the canon was the HS. We are told that. But I think it was more indirect than you do. I believe that the HS lead the apostles and their immediate successors in the right paths and that their teachings became part of the fiber of not simply that “catholic” church that +Ignatius of Antioch wrote of, but also of the People of God themselves. In living their faith within the Eucharistic/Liturgical communities which they were part of, they were transformed by the indwelling of the HS and a common belief was received and accepted...what “The Church always and everywhere has believed”. Its that corpus of beliefs which was the yardstick used to determine what eventually became the canon of the NT.