To be fair, looking at the setting of the game, Larsa can get away with being smart. As the son of the Emperor, no doubt he had access to the highest and best forms of education that Archades had to offer. Likewise, being of a ruling family, it only makes sense if he has insight in politics, and was no doubt taught them as well, given that politics were the most likely reason why somebody might try to kill him.
I agree. I think Larsa seemed well educated rather than being overly intelligent. The child genius archetype tends to get into trouble due to trying to do too much, like Penny from Inspector Gadget or something, right?