I know it depends on the show that is playing, but are there assigned seats for an orchestra show? Or is it first come, first serve?

I've personally never been to the Fox for a first-come, first-serve basis event

I have always had to get the seats and are assigned however you can probably move if no ones near you

I think it's always reserved seating.

Assigned seats always!

If anyone has a student ID they can go to the Box on the day of the show and pay $20 for best seats

I've been to a variety of types of shows there and always had assigned seats.