World Without an Arab Muslim Conquest of Persia

For the past few years, I've been imagining what Iran, Central Asia, and much of the rest of Asia (as well as parts of Africa and Europe) would have been like had the Arabs not managed to conquer the Persian Empire in the 630s-640s. This is a much more complicated alternate history than what I've been thinking for Argentina and neighbouring countries for the past 5 years, so it's been very much evolving. What you see below are my rough sketches of what would have happened in this universe (and what did happen in another universe). The point of divergence for this is when the Persians beat the Byzantines at the Battle of Nineveh in 627, and not the other way around. The Persian Empire then remained fairly strong for some time, though Mesopotamia became Arab/Muslim later anyway.

One of the most important consequences of a Persian repulse of the Arabs is that Zoroastrianism and Nestorian Christianity would be much more widespread religions than is the case today. Persia would have had a Zoroastrian majority for a long time at first, but more and more people would have converted to Christianity given that the Persians became tired of fundamentalist Sassanid Zoroastrianism, as well as for other reasons. Either the Sassanid dynasty would have converted to Christianity, or there would have arisen a new and Christian dynasty - both of these possibilities taking place around 750 CE. Iran would have a Nestorian majority today with a 5-10% Zoroastrian minority as well as other minorities (including Muslims along the Persian Gulf coast and around Ahvaz), much in the same way that Egypt is majority Muslim but has a 5-10% Coptic Christian minority.

Central Asia would be largely Nestorian, with some pockets of Buddhism, Zoroastrianism, and other religions. The Turks convert to Nestorian Christianity rather than Islam; hence, assuming that the Turks still carry out their conquests, countries like Turkey, Bosnia, and Albania would have Nestorian majorities. At the same time, much of Afghanistan and Pakistan (as well as Bangladesh maybe) would be Buddhist.

Also, I am assuming that Arabia, the Near East, and North Africa remain Muslim. In that case, there would still be Sunnis and Shias, but there would be many more Ibadi Muslims too. Finally, I'm assuming that the Mongols are conquering just like they actually did.

Of course, there are still plenty of questions to ask and details to iron out, but hopefully this should represent a first portrait of an un-Islamic Iran from the 7th century and long-term consequences around the world.