The Narnia films were a big part of my childhood, but I havent seen them recently.
From what I can remember, Miraz was a perfectly competent villain in Caspian. I especially love the infighting between his generals, showcasing how his court is filled with opportunists who value power above loyalty.
The real villains of Prince Caspian was the Telmarine culture of conquest and dictatorship. Caspian wasn't merely fighting his uncle, he was fighting his legacy.
In contrast, Voyage of The Dawn Treader is in book form just about the journey to the end of the world. Their different stops are various learning experiences that helpthe characters grow.
The Dawn Treader film reused the White Witch because she was the manifestation of Edmund's struggle with temptation. It provided a nice throughline for the otherwise pretty thematically disconnected stories.