You are correct about the hero decks available from this campaign. Having unbalanced teams is not against the rules in a game breaking sense, it just wouldn’t be fair. You can do up to 5p if the map supports it. The Adventures maps support up to 5p.
Heroes have sidekicks, villains have minions. Sidekicks always fight with the same hero. Minions can be used in any combination with any villain, they are only used in coop Adventures.
This Adventures set is compatible with Unmatched Adventures: Tales to Amaze so there are now four villains who are each used on their own board, with any mix of minions (from either set) and can face any combination of heroes from any Unmatched set.
Yes, allies and henchmen are just cards, no minis.
Heroes have sidekicks, villains have minions. Sidekicks always fight with the same hero. Minions can be used in any combination with any villain, they are only used in coop Adventures.
This Adventures set is compatible with Unmatched Adventures: Tales to Amaze so there are now four villains who are each used on their own board, with any mix of minions (from either set) and can face any combination of heroes from any Unmatched set.
Yes, allies and henchmen are just cards, no minis.