Track #1 is the EZdrummer instrument, and tracks #2 and #3 are just used for MIDI that is routed to the instrument on track #1. Here is a really quick example of using two extra instrument tracks that each send just one MIDI part to play in EZdrummer. Or you could route multiple MIDI tracks to the drum plugin, and record each part on a separate MIDI track. Drum plugins generally use just 1 MIDI channel, with each kit piece assigned to a different MIDI note according to the 'drum map' being used, so you can record all drum parts on the same MIDI channel, as you have noticed.
