Unless your home airport is a hub of one airline, my guess is that you'll be taking a different airline for each trip. Google flights and/or kayak is your best friend as an MS4; you'll be spending more on interview travel than you think. Hopefully you're applying into one of the few specialties that still covers hotel rooms.

As for the cards you mentioned, the CSP is probably the most versatile, has the best signup bonus and is easiest to use the points. At the end of the year, if you find you're not getting the 2x points enough of the time (I average about 1.6 points per dollar every month) then you can always switch to one of the others.