You can pick one of two game modes in the beginning of the game and only change it by doing a full repick:
Freelancer: Starts with increased attributes and gains XP faster but cannot build up a base with any race but only a Hideout and some neutral buildings.
Warlord: Allows picking races and build up a base with a high food limit but gains less XP and has lower start attributes than Freelancers.
Game settings also have to be chosen in the beginning of the game.
Some of them can be changed during the game with votes.
Tomes enabled "-tomes/-notomes": By default this is disabled since it can lead to a pretty unbalanced game if one player has more gold than others. If you enable this setting, players are allowed to buy tomes in neutral shops. Tomes increases their hero stats. However, these stats won't be stored in savecodes.
Unlock everything "-unlock/-lock": Unlocks all races, heroes, professions etc. which means your heroes do not have to reach a certain level for locked content.
Enable Savecodes: Allows loading savecodes. Players cannot load their savecodes if this setting is disabled.