The thing about Thrawn is that he doesn't have a "habit". He adapts and plans. If he encounters an enemy that seems invincible, he creates tactics to beat him. In the case of the Thrawn Campaign, he had laid out the path to victory, executing each step to perfection. The New Republic had no idea what he was planning next.
Don't know who could beat Thrawn. IIRC Admiral Bwatu of the Galactic Alliance beat the Thrawn Simulator consistently. But I don't think a simulator can match the real deal.
I think beating the simulator makes him a good tactician either way. It may not be the real deal but it is close enough for him to be a good challenge imo.