I'm going to rehash things about Sirius, going further from this post!
I absolutely despise seeing fics (not naming any because I purposefully avoid a LOT of Marauders Fics for this reason) where Sirius has been made this overly sweet/emotionally intelligent bimbo/twink, where the authors also ignore The Prank or they make it out to be an 'accident' with no real consequences in Sirius' social life.
The Prank, I think, gives such an interesting insight into who Sirius was as a character, especially since it's one of the only canon aspects we get of him.
It shows us that Sirius can be cruel. It shows that he finds enjoyment in pranks that do have real life consequences for other people, and it shows that he will do whatever he wants to the people he really doesn't like, which in this instance, is Severus. We see this throughout Sirius' adult life, too, where he is constantly jabbing at Severus, calling him names - acting totally immature for a grown man, Azkaban consequences aside.
With this, we can deduce a few other things: He wasn't very emotionally intelligent, most likely, and that his upbringing likely affected him more than he cared to admit.
While I think he would be able to recognise and (probably unhealthily, lets be real here) deal with his own emotions, he absolutely either would not realise, or care about other people's emotional responses to his words or actions - Hell, he didn't about Snape, so why would he about other people, especially people he didn't know?
If it got results, he would do it. He was known to be a prankster, and was seen with James in the memory Harry see's to have been a bully. From this, we can easily see that Sirius (and James, at that point in time) liked garnering emotional reactions out of people. He enjoyed the negative reactions, he enjoyed making people feel small.
As for his own emotions, as a quick side note, he would probably be able to tell when he was feeling a certain way, and what the feeling was, but push it aside. His upbringing would have taught him how to be the charming man many people considered him, and would have likely made that charm about him be a total mask, more than anything - and, in my opinion, it is likely a mask he never really took off, either.
His upbringing, on that topic, is something I also see a lot of in fics as something I do not resonate with. I truly do not think that Orion and Walburga were physically abusive. Of course, there must have been one aspect of abuse that would have made Sirius want to leave the home for good, but the abuse doesn't always have to be physical, people.
I believe that their love for Sirius (and Regulus, for that matter) would have 100% been conditional. They are from the Most Ancient and Noble House of Black, in the Societal Elite. They had a reputation to uphold, and that reputation would have, in my opinion, easily dictated how Walburga parented her children - as I do believe Walburga did majority of the parenting in that house, as I don't remember Sirius mentioning Orion at all.
I believe he had so many expectations on him as the heir. Expectations that, before he ended up at Hogwarts, felt easy to accomplish, easy to live up to. Once he got to Hogwarts, and was able to start thinking about the world in an area with multiple ideals and such around him, as well as being able to physically see different perspectives of life playing out? I think this is when his relationship with her turned sour.
Now, that doesn't mean I think Sirius hated her. Sure, he says he does (i think. don't quote me on that), but I really don't think that's true. I think he wanted to be able to prove himself to his mother over and over again, and could never win, because their views on the world stopped matching each others by the time Sirius was 12. I think that Walburga got harsher with her words, cutting deeper into him, and maybe she started insulting his friends - maybe James, as canonically, one was never seen without the other - and he lashed out, and started to rebel. (every teenager rebels. it doesn't have to be because of abuse).
However, this upbringing: Being taught the Pureblood ways, living in the Societal Elite for most of his formative years, would have stayed with him. I think he has an air to him that forever screamed rich, even after being disowned. He would have gotten what he wanted, no matter the cost. He would have been taught how to do this, too, hence the charm everyone mentioned in canon.
He would have been brought up like a Slytherin, because it was expected of him. I truly think he never even considered not being in Slytherin until he met James on the train. I truly think he was happy enough to follow in the footsteps of his family, of walking the line drawn out for him before he was able to walk, until he started school, and started being able to think for himself, without his mother influencing those thoughts.
Sirius wasn't some twinkified teenager who loved everything and everyone around him. He was cruel, he was cunning, like a Slytherin, he was charming, and he knew exactly what he was doing, at all times.
