Closed = nothing but name, and maybe home location. (UCSF was closed)
Semi-closed can mean anything, OHSU had everything but my MCAT and Grades.
Open is open.
That said, don't let the interviews affect your primary, secondary writing topics. Choose the most compelling and interesting topic for your primary... this will open the door to interviews and determine weather or not they choose to read your secondaries at all. Note that secondary questions vary from school to school, so don't count on being able to use the same/similar topic across the board. Also, if its a closed file interview, then you'll tell it all again anyway. If its open file, you'll enlighten them on the various details of what you wrote/tell it all again (b/c sometimes they don't read/retain what's in your file). Regardless, just write something super-compelling for your primary.
Hope this helps,
-OFD