ScienceOne, yes you can user s USB->MIDI without a joystick in your computer (I use one in my laptop). As for the second question I think you are referring to the possibility of running ur MIDI leads straight into your multi-effects processor... the only way that this would be possible is if the processor had some sort of MIDI 'Sound Canvas' in it, other than that I think the only way this would work would be to run the output from your sound card or a 'Sound Canvas' into the effects unit and record it at the same time back on your computer.
I hope this helps,
Porter