In a scenario where the West Slavs, Scandinavians, Balts and Magyars go Orthodox, long term knock-on would be interesting.
Despite probably some temporary occupation by Orthodox Scandinavian rulers, England will probably remain loyal to Rome. Even if their homeland of Denmark is Orthdox, Normans in Normandy, England and Italy will probably remain loyal to Rome.
There is going to more of a cultural divide between the Germans on the one hand and the Poles, Czechs and Hungarians on the other. The Orthodox Tsars of these states in the medieval era will worry more about spiritual contamination by German merchants and craftsmen who they encouraged to immigrate in OTL. They may try to poach more Greeks with comparable skills. On the other hand, they might be fairly trusting of converts, leading to Germans immigrating and probably basically assimilating into Slavic and Magyar societies as they convert when they emigrate and start hearing slavic liturgies in church all the time.
Butterflies will prevent the western schisms and reformation for occurring exactly as they did. But supposing there is a rough analogue of Reformed thought after the invention of printing, I think a completely successful "counter-reformation" in the historic western Christian zone (northern Germany, Netherlands, England) is fairly likely. With Hungarians, Czechs and most of all Danes and Swedes as uninterested, Orthodox "neutrals" in any schism among western heretics, the alternate version of the Protestant side won't have key geopolitical support to survive the reaction from those loyal to Rome. Certainly not in Germany, Netherlands and Switzerland. Perhaps, just maybe, England could make a break with Rome stick.