2 was easy to manage because obviously it's just A and B. 3 wasn't much harder but that was definitely a campaign where it was one main faction and the other two were supporting ones, there to act as foils and so on.
Both 5 and 6 games were actually me being the GM for multiplayer campaigns. On one hand it was easy because the players would come up with all the names and themes and would write RP snippets about the games. On the other hand, it was really difficult to keep all players well informed at all times since we couldn't pass the DB around. Both campaigns ended before we even left Sol because of issues but also the players fighting each other.
And now I have the C# 1890 campaign with 10 factions. It definitely requires a certain amount of standardization - like all the ground formations are similar, as are naming conventions and I don't bother with much narrative about individuals because keeping track of them would be a nightmare.