can you link the video?
in summary, currently Bannerlord has:
In captain mode (multiplayer) you choose a class and control a group of AI soldiers and battle other players, you will only have acess to one type of unit
in campaign (singleplayer) you build an army and battle against AI lords you control multiple types of units (archers, infantry, cavalry)
in custom battle (singleplayer) you also control multiple types of units, but this time you dont have to go through the whole process of building an army
hope I helped