Jack Welker's hairstyle is different from his gang members', and probably different from anyone else's in Breaking Bad serial. Does his hairstyle have any specific meaning, like his status as a gang leader, or something about his background?
While the Breaking Bad writers have been known to use a lot of symbolism in their show, I think this is just an instance of fashion choice. Jack Welker's hair style might be different from the rest of his men, but it's not particularly distinctive. The slicked back look is a common one, especially with older people who have long hair. So the fact that Jack is just older than the rest of his men might account for that hair style.