I'm trying to find out if this product allows me to use ANY model Gtr (Whether it's IK Mult., or Studio 1 models) WHILE using the Patterns, or FX from Session Gtrist?
Not that I know of. I use my Session series ll the time and they are all self contained.
That said - a couple of the VERY recent instruments allow the user to drag and drop MIDI (like @ 1:20) of this video:
Session Guitarist – Electric Storm Deluxe walkthrough | Native Instruments
But that is as far as the "sharing" will go.
VP