Here's what helped me when I prepped for some interviews this year and last year:
"Why this school" and "why playwriting" should be the two biggest things you focus on. Your essay and writing does the heavy lifting, schools just now what to put a face to the name, see how you hold yourself and how you talk about yourself and your writing. You don't have to justify your entire existence as a playwright in only 10-15 minutes, but focusing on the main bullet points about how/why you found yourself trying to make a career in theatre, and why you want NYU to help you get to that next stage in your development.
I would also focus on the questions "what do you have to work on in your writing" or some variation of "what do you struggle with" is not only commonly asked to students interviewing into a writing program, but also most job interviews on the planet. I think people like people who are self-aware and self-motivated to get better in areas they already know about.
And then, as always, make sure you have questions for them! Even if it is something as simple as "what's the student to teacher ratio", any questions you have about the structure of their program goes along way in showing to them that you are thoughtful and meticulous when planning your future.
Break a leg with NYU! Here's hoping you hear positive news from them, and quickly!