Johnny most likely wouldn't have turned himself in because he knew the other boys would react incredibly depressed. Johnny holds the group together and is the weakest. They feel as if they need to protect him, but if he gets sent to prison, then they would feel like they failed him.
If he was a soc, he most likely would've cared less since they're rich. They would possibly be able to pay him out of jail time.
It would matter because he wouldn't have to worry if he was a soc. But he's a greaser, and he has a group that feels the need to be his guardians.
In today's world, murder isn't exactly able to be payed out of. If he was a soc in jail for murder, it would be extremely popular on social media or the news since he would be coming from a rich family. If he was a soc that committed murder, it would matter less, but it would increase the already-bad reputation of the greasers and the people living in that area.
