Impostors are a key component in Among Us. Most lobbies in Among Us have 2 impostors but there is an option where 3 impostors are also possible.
A game with 2 impostors gets pretty challenging if the two of them are good at what they do. Good impostors can easily dominate the lobby of 10 people without batting an eyelid. In such scenarios, having another impostor would make it even more difficult for the crewmates.
10+ player lobbies in Among Us
Having 3 impostors in a 10-player lobby makes it easier for the impostors because all they need to do is take out 4 crewmates and they win the game.
So perhaps 10+ player lobbies would be better at accommodating 3 impostors. That way the game would also become equally challenging for the impostors. They'd have to dispose of more crewmates than in a 10-player lobby and be more careful.
Impostors win the game if the number of crewmates equals the number of impostors. So disposing of 4 crewmates in a 10 player lobby would bring down the number of crewmates to 3 which equals the number of impostors.
In comparison to this, a lobby with 2 impostors would have to kill 6 crewmates, and a lobby with 1 impostor would have to kill 9 crewmates in a game of Among Us to win.
At this point, expecting a larger lobby may not be feasible because the Innersloth team is working on many different aspects of the game. Based on their recent patch notes, the team is working on a new map and the accounting system is Among Us.
The latter is very important at this point because that would make it easy to add friends and also report and ban accounts that run hacks.
At any given point in time, larger player lobbies would make more sense for a larger number of impostors. But for a 10-player lobby, a maximum of 2 impostors is best, at least for now.