If I want to make use of my Greek Fire, I do not need the War Engines trait right? It's usable on jsut basic siege equipment?

Also, if we want to deploy siege engines on the battlefield and not necessarily on an actual siege can we without the War Engines trait?

Plus, you said that commanders that are killed can be replaced but with lesser skilled ones, does that mean the point cap remain the same. Say if I lost a Celestine Hero of the Realm I can replace them with 2 Lords/Commanders?