When I interviewed last cycle, my formal interview had multiple people. If you have more than one interviewer, it's likely that the other person is there to train so that they can start doing interviews on their own at some point (they'll probably tell you that person is training as a heads up). About MMI, I was actually pretty intimidated by it if I'm being honest! But I think that was because it was my first MMI exposure of the cycle (my next interviews with that format felt smoother since I knew what to expect and how to better keep my nerves in check).
I'm also a current M1 here! Feel free to DM if you have any itching questions or if you're too shy to ask in the forum
And congrats to all of you for making it this far!