Congrats on the interview! More of a general tip, but the ED interview was framed to me as they've already assessed your application and believe you're prepared for the rigors of medical school. The goal is to show your personality, your communication skills and how you'll fit in their community, not so much prove to them why you deserve a spot. Be honest and have fun. If it's a tougher question or you feel yourself getting off track, you can always ask them to clarify, check-in and ask if what you said answers their question, and offer to elaborate on any aspect of what you've said.
I don't think who the interviewer is matters too much, in fact it may help the conversation to know less since you can come up with more genuine questions to ask about their background or what advice they have for incoming medical students at the end, but one suggestion is during your morning check-in, when they ask if you have any questions, ask if they have an email on file for you interviewer so that you can properly thank them for their time.
Last, if it's for ED, you could always reach out to one of the deans of admissions to reiterate your excitement for the opportunity and ask for their thoughts on what you can address further to strengthen your candidacy. They probably will have some good insight.