Hi CrossFire271 - we're working on a single player option for a future update, but you can create your own server and play solo. It's good for practicing stacking, but not as chaotic as playing with someone else :)
With the additional players, there *shouldn't* be too much difference between having 2 players and 12 players - definitely join our Discord, and we can get a time sorted to join in with you in a game!