Ah, thanks for the patient response I must've come off a bit polemic.
Yes it is true that in Buddhism there's no explicit banning of other gods, and there's definitely no point in arguing semantics but for all intensive purposes it's still probably better to call it agnostic to the idea of gods as opposed to polytheistic

.
Any sort of Christianity in China is definitely going to inherit worship of Confucius, ancestor worship, some local customs and rituals (each village will likely syncreatize them) and perhaps even more explicit alterations of the trinitarian doctrine. The guy who led the Taiping Rebellion claimed Jesus was his brother

. It's just too far for regulation by the Catholic church, so Christianity in China is going to
likely be very different.
I don't actually think that you don't need no Buddhism for a Christian China. They don't really wouldn't conflict a whole lot, and many Christians can still follow Buddhist traditions and ideals- much in the same way post-1300s Taoists and Buddhists got along despite being almost fundamentally opposed in philosophic tenants. Most important is the preservation of the Eastern Churches. A Christian Persia, a surviving Bactria that adopts Christianity, a No Islam PoD or Nestorian Mongols (or any of these just for a brief 1-2 century window) would all fufill the minimum needed to probably engender an eastern Christian class in China. Iotl there were Eastern Christians in China they were just so few- in the thousands, that nobody really gave them much notice. Give any of the latter their time of day, and you'll have a Christian Hui develop out of contacts along the Silk Road.