Congrats on getting an interview - sure you will smash it.
My advice is to still keep it business professional - you can always dress smart and then tone down (i.e remove jacket, where a sweater etc.) if needed. Most offices don't have mandated dress codes but Bainees usually wear business professional as they can often be called into meeting clients at short notice.
Business professional clothes can also vary by office a lot - on the west coast might be shirt and jeans whilst in London/New York it is always suit. Hence tailor this to your geography.
The advice is to remove any unconscious bias in the interview - interviewers are human and hence can have biases. My advice would be to always project a professional image as you cannot guarantee the age, profile of your interviewer.
Good luck with the interview!