OK, so I literally just finished a 27-lecture run of a human behavioral biology course and am therefore very dangerous. HOWEVER, some of the stuff you're describing here sounds a lot like a possible variation in dopamine processing / dopamine receptors. There are different kinds of receptor, and it's hard to find plain-English articles on this but the professor said that can make a difference in what a person finds rewarding, how novelty-seeking they are, etc.

I am mildly vindicated in this by finding an ADHD section in the otherwise bad Wikipedia article on this topic:
https://en.wikipedia.org/wiki/Dopamine_receptor#Attention-deficit_hyperactivity_disorder

but smaller individual variances are possible and common!