There should be 2 interviewers, a clinician and a researcher. (conducted separately) but they might not ask solely research or clinical questions. (for example, the clinician can ask you about your research experience or how do you foresee research being part of your medical career. and the researcher might ask you what are your motivation in making this decision to pursue medicine.)
There will be staff guiding you to the correct room, you can ask them for the interviewer's name and if they are clinician or researcher (though it doesn't really matter).
The interviews are not too stressful, they are quite friendly (or at least those that I have gotten).
All the best for the applicant day!!