You may also find interesting (and you likely already know of this) the existence of “Nesotorian” Christianity within the Mongol tribes of the medieval/late medieval era. This is a key aspect to the diplomatic outreach between the Mongols and the West towards the end of the Crusades. Additionally, it likely played a role in that era’s equivalent of “fake news” spreed regarding “Prestor John,” a supposed Christian King of the “East” who would come to the Crusaders’ rescue in their hour of need.
These aren’t exactly “theological” takeaways, just fun things to learn about relevant to the Western world’s interaction with Eastern (as in, to the East of the “Orthodox Church”) Christianity. I suppose some of the above information above all else shows how poorly misunderstood Eastern Christianity by Western “Christendom” has been, historically speaking.