Yes, you can
use the XS while in Remote Mode.
First, you can toggle in and out of Remote Mode (which takes over the XS screen) at any time, unless you are currently in either Song or Pattern mode with the XS sequencer running
. Since you use Live to do the MIDI sequencing you'll have no problems toggling between modes.
If you have the XS in Song or Pattern mode, it can be used as a multitimbral sound source. You can use Live's External Instrument
but at some point you will have to record into an audio track. I just use individual MIDI and audio tracks since I will end up recording the audio eventually anyway.
What audio interface are you using? If you have the onboard FW for your Motif you can track up to 16 channels of audio over FW, makes it easier to put parts on individual audio tracks. If you don't, you will have to record each audio part in a separate pass.
BTW if you do
have the FW interface, once you have recorded the audio you can use the XS master effects as an additional processor for Live...very cool
If you have specific questions, let me know.