as for moving track order directly in mixconsole,i saw a topic where helge says its not yet implemented which means they are going to do it i future i guess.
as for the subject. the midi channel as nothing to do with the actual audio output signal of that vsti.
think the vsti in rack as an hardware synth, u use the midi track to sequence(record the midi info) and that synth(or vsti) has also other audio output that goes to audio channel to hear it.
on the other hand Instrument Track is combined, u can record midi to it and also the audio output is there, the disadvantage is of course that is limited for one voice/output. so u cant use for example record/use more then 1 channel in multi timbral vsti as kontakt. see here the differences.Cubase 5.5: Instrument Track vs Midi track - YouTube