Hello, congrats on your interviews! I know what it's like to have to travel for them. As a bit of background I'm a final year medical student (about to start my preinternship) at the moment so i can probably give you a bit of insight as to dressing and packing.

Reading the one bag ninja thread is a nice start but it's definitely on the more extreme side of efficient travel. If you feel comfortable checking a bag with extras there's nothing wrong with having the bare essentials in a carryon then checking a bag with luxury extras. In terms of what I think you need, a few of the folks above mentioned that you should take the interviews more casually. I vehemently disagree. You should view these as job interviews and as such, you should wear that suit and tie. Just the one set of business attire should be enough. After that I would pack 2 extra sets of casual clothes, something to sleep in and the rest of your essentials. A garment bag (that Gate8 trifold) would be pretty much perfect for this task.

Dressing like a med student, I wear a business shirt, dress pants and dress shoes with no tie (infection control). I suspect you'd get away with being pretty casual in a social situation outside of interviews, I walk around in jeans and a T shirt on campus...

Best wishes.