The Third North African Council that canonized the Christian Bible was a local Council and therefore not binding on the whole Church. The Eastern Church referred to the Revelation as questionable until the end of the 8th century. The Orthodox Church to this day does not liturgically read from the Revelation, the only NT book that is thus excluded.
Obviously, not all dogmatic pronouncements are based on the exact number of canonical books. I submit that, without Hebrews or Revelation, nothing would change dogmatically as regards the concept of the Triune God, the dual nature of Christ or Mariology.
Both Churches make that very clear and reiterate that the Church teaching is as much based on what's in the Bible as in the unbroken life of the Church liturgically (Eucharistically), in other words lex orandi lex credendi.
Yes, that is the important point. We are all tolerant of even significant differences in the understanding of the Canon (in the West the Revelation is used like any other scripture; some pre-Chalcedon Oriental Churches have extra books) so long as the doctrines are compatible if not identical. That is because we all, East and West, view the Holy Scripture, as well as the patristic writings, not as the source of doctrine but as a consequence of it.