<aside> 👉 This is a guide about how to join or organize a game of Old World with others. If you are looking for a winning strategy check out Multiplayer Strategy Guide by @Fluffybunny
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Old World was designed iteratively from the multiplayer experience first. It is a fairly balanced game where skill matters a lot. Randomness is contained to events and characters mechanics, which are optional in a multiplayer game.
The two major formats of Old World multiplayer is Network and Play by Cloud (PBC). The network game makes sense when players have two-three hours of uninterrupted time. A cloud game usually means a turn a day and requires commitment over few months (but just a few minutes a day).
Cloud games often played on huge maps, FFA, seven or more players. There is no time pressure during a turn, and it may open many opportunities for in-game diplomacy (would there be diplomacy really depends on the players though).
Network games typically will be duels, 2v2, three-player FFAs. Playing a network game with teams combines fast-paced collaboration with competition and is probably the most balanced format. Network games usually are time-pressured with a minute per turn timer.
While these formats may feel very different for the players, the game rules are the same. Moreover, a network game could be moved to the cloud and later back to the network.
Unfortunately, there is no ladder for OW at the moment and Cloud games require a host to get account names and emails form each player. Finding the players of similar level and arranging a game could be tricky. This is why this guide exists.
Usually, it is the same rich Old World experience. Initially Soren designed multiplayer without characters and related randomness and it is still an option (notice that it is turning off a lot, including families), but most players prefer to keep the characters on and only reduce frequency of events to "Low".
Thus the difference comes from the fact that instead of upstart nations surviving and then overcoming massive AI nations (the storyline of in the single-player mode), you compete with symmetric to you opponents controlled by determined to win human players.
The maps are smaller and a chariot rush with Persia is a valid strategy.
The Ambassador is less important early game, and their bonus goes towards families instead of other players.
The metagame of Old World constantly evolving, some current observations: