I thought Chalamet was pretty good at playing Paul, but I felt the character should have been written a bit more naive at the beginning. It was always my understanding that, yes, while Paul grew up the heir of a royal family and was trained for such, he was still a kid.
As soon as he reaches Arrakis, when House Atreides goes down in flames, and culminating when he and his mother are in the tent and he’s exposed to the spice, is when he becomes more “edgy” and serious.
Maybe it’s just me though. I’d have to read the books again, it’s been a while.
Actually that’s the whole point according Herbert himself. Paul is essentially this super-human who’s had the best education, both intelectual and martial, that his noble status can afford, is pretty much a human supercomputer, has the best possible genes of any human being, gains the genetic memory powers of the Bene Gesserit and he still fucks up.