Regarding Yankeeland coinages of varying degrees of well-knownedness, my impression is that “yinz” is known (and often used) primarily in a very specific region, whereas “y’all” is another second person plural pronoun that is also regionally used, but more broadly known. (though sometimes “y’all” is singular, and you need to say “all y’all” to make it plural…)

I should probably stop now before I get accused of going ham on grammar.