"Acting white" is a black concept by definition. But poor whites absolutely do have an analogous cultural stigma: the concept of 'showing up' your parents/family/friends by doing better than them. You may have also heard this expressed as 'thinking they're better', general discouragement of learning, some uses of 'putting on airs', etc.
As for role models, it's more important for minorities to see people like themselves in those roles, strictly because culture is otherwise telling them there are things they cannot and/or are not allowed to do, because of who they are.
It's not that a would-be black scientist needs a black scientist to be inspired to pursue science. Nor a would-be gay politician needs a gay politician to be inspired to pursue public service. It's that a would-be black scientist or gay politician benefits from seeing anyone like themselves doing what they want to do, so they can know our culture is full of shit when it says they can't.
It's far, far easier for a child to believe the lies and be discouraged from a challenging path if there is no evidence out there to disprove what the culture is telling them.