OOC: Wow, even a bit of Europe is a high demand.
IC: One major divergence would be the philosophical duties of the ruling class. The vikings didn't really conquer anywhere but England, Alba, Eire, Saxony, and Frisia, and even that is largely due to luck. The Frankish Empire was splintering between Charles the Great's sons, Charles the Younger of Francia, Pippin of Italy, and Louis of Aquitaine. These kings and their descendants warred with each other for the control of Charlemagne over the entire Empire. The chaos was great enough that vulnerable areas just overthrew the Franks and installed Nordic leaders as their rulers instead of getting raided, and as things got worse more and more areas did this. In cooperation with viking supporters, the local peasants just overthrew their feudal nobles and replaced them with said vikings. Tribute became taxes, and so Europe was 'conquered'. The people just basically handed it over in return for peace and protection.
It was this series of events that really changed perceptions on rulers. The Frankish feudals lords that dragged whole armies as they waged wars across the Empire were replaced by foreigners who were only installed by the local people. The Nordic leaders never quite forgot this, and those that did became lessons for later generations as they were themselves replaced by newer and more understandable ones. While conflict between the Nordic ruling classes remained till the Golden Age of the Nordic System, it was by necessity far more personal conflicts. Competitions and rivalries between the Jarls with their huskarls. Not armies. The sort of fights and quests immortalized in the Sagas as befitting rulers, and the people themselves decided dealing with this was better than what came before. They might end up with a different ruler because he defeated their previous one in a wrestling match, but at least they didn't die for it. This established the democratic, meritocratic, and even elective system that lasted till the 1500. The Golden Age became so because the Udvandring system and this peace encouraged period of population growth caused the rapid settlement of Vinland and Overhavet, providing an outlet for the excess nobility to earn lands and titles instead of competing in Europe for a limited number.
There's a reason this Age is so romanticized. Nordic nobles exploring these vast lands in bold journeys, their interactions with the Skraelings, the accomplishments achieved to make a name for themselves as worthy of following. None of this would have happened if the vikings never achieved success, instead feudalism would have continued. Rulers who inherited their positions, fighting their own siblings with massive armies to reunite the divided lands of their fathers, etc. Without nobles who needed to prove themselves and thus spent their fortunes on exploring or building, competed with each other on a personal level for personal glory, Europe would have been too consumed in conflict to ever expand.
Although they might have avoided the hilarious events of the century following the Golden Age when the Nordic nobles weren't capable of understanding the East didn't follow such traditions. The number of nobles who died from comparatively silly things really just comes across as inept. It wasn't till around 1500 that the Nords were ready to try again, unfortunately by this point the developed settlements in Vinland and Overhavet alongside the unfortunate changes in leadership style by the Nordic rulers would bring about the more dismal times of the Age of Colonization.
OOC: So my POD is Charlemagne not being lucky enough for two of his sons to die before him, thus leaving Louis the Pious his sole heir. So the Frankish Empire started fracturing earlier, and this early decline meant Frankish feudalism never stopped dividing the lands of the father between all the sons. Really gave feudalism a bad name. Otherwise, I was just amused by the idea of noble feuds playing out in this time like the weird challenges of the Sagas. You know, 'he who kills this beast will become king of this land or 'this princess will marry the one to win this series of Olympic-like events'.