Hello,
I am a little confused as to what your question is, so I will try to answer it as best I can. I think you may be confused about what VSTi's are and how they can be used.
VSTi's or virtual studio instruments are both
audio sounds and midi data. For instance you could play the B4 (excellent B3 btw) and record the audio output from your soundcard as you would any other audio sound. This would be using the VSTi in a "stand alone" application....Or, In Cubase you open up one of your VSTi's and it is automatically routed to a channel on your Cubase mixer. There you can add FX/Panning/automation or whatever.
Once you hit record the sounds are then recorded as midi data also. From there you have a whole host of midi editing options at your fingertips.
The VSTi's can be very CPU hungry so once the midi track is done, I useally export
the track as an audio/wav file. It works great for me. The exported midi track pops up as a WAV file in the exact same spot in the song or arrangement as the midi track used to be...cool.
A great resource for VSTi info is
http://www.kvr-vst.com/
The site is updated almost daily and has a lot of "free" VSTi's available for download.
Hope this helps...
simonsez