Priscilla uses Cardi B sound bytes because Cardi B is an an abrasive, unlikable, overpaid and overrated hag with an overinflated ego who has been given a mouthpiece by a wayward society, which she has used for no good purpose, and that resonates with Priscilla.
Yes, it's supposed to be funny, cool, hip, etc ("supposed to be"). The Maasses are the types of parents who are preoccupied with being perceived as "cool." I don't know why, but some parents are like that.
I'll have to respectfully disagree with MaidenX and say I don't think the Maasses are actually being racist or bigoted. The reason it comes across so poorly with the Maasses is because they're so embarrassingly bad at it. If they could pull it off it would just be amusing, but because they come across really dorky when they do it, it comes off like they're being insulting.