If I had to guess, probably had next to no control in the beginning. Growing up in a family in such close social standing with the Pharaoh had to have been seriously regulated, and if he displayed a knack for magic at an early age, that most definitely shoehorned him into study right off the bat. Even if he wasn't a naturally focused individual, slacking out of the role would hardly be a socially acceptable possibility. But being that specific individual, I don't think he was ever particularly unhappy with his role.

In the end though, I think he made a good measure of freedom for himself last minute. His endeavor to chase the thief king was of his own volition and in spite of the court's better judgment, as was his decision to sacrifice himself and become the Pharaoh's eternal servant. Which, really.. continues to lead his life down whichever path Yugi takes with the Dark Magician. But he chose that isn't that what counts..........

lbr maybe that's probably why he was never allowed to make his own decisions