He's a year older than in canon, so he's 17 during the alternate version of the show's events. He also looks a bit ambiguous visually, where although he's clearly young, he could be read as anywhere between 16 and early 20s.
Now, about his personality.
Due to growing up with not just one, but two loving father figures, he's more stable and confident. He does still have insecurities, but they developed out of wanting to live up to Anthony's (previous Golden Guard's) legacy, worrying that he can't, and feeling like Belos thinks he's weak - an impression he got from Belos's protectiveness.
Rather than trying to broadly prove his worth, he was specifically trying to prove his strength. He believed that he was being underestimated due to his lack of natural magic, and he wanted to prove that he was capable.
As the Golden Guard, while he did have some amount of ego and believed he should be treated with a certain level of respect, he also believed that it was his responsibility to serve the best interests of the Boiling Isles. He cared about the well-being of the people, which is why he ran away to join the rebellion after he learned that Belos was lying about speaking to the Titan and that his plan to unite the realms was extremely dangerous and likely not going to work.
He was more performative when wearing the Golden Guard mask and playing that role. He was more sassy and snarky, and he tended to show off more. Without the mask/as his normal self, he's typically more reserved and pragmatic, not bothering with theatrics.
While he's clever and well-trained, this does not mean he's not susceptible to provocation and to making ill-advised decisions as a result.
He tends to correct people's mistakes when it's related to a subject he knows a lot about. His interests include mechanical engineering and tech, which he has been studying for a while, inspired by Belos, and the more recent additions of wolves and Cosmic Frontier.
#tohAU #RLAU
A bit about Hunter in this AU.