There's not really a heirarchy. There is generally 10 or less "gangs" that a lot of people are in, and even those don't usually have a heirarchical structure. The point of these crews is that IF someone messes with one person in them, they are messing with the whole crew.

In prison, whoever the toughest guy is doesn't really matter, it's whatever gang that you don't want to mess with (i.e. - is most likely to beat the [censored] out of you / anyone you talk to). An individual person does not matter.

Connections? Well, about half the people in prison have a connection on at least something. Generally the latin guys have FAR more connections on more/better things though. Not really sure why. Here again is another reason for the crews: stepping on the toes of someone who has a specific market cornered AND is part of a crew is a good way to get your ass kicked.