Digital BW, The Print

I have been trying to develop a work flow for the above hardware using Windows 7 and CS3.  As per Paul Roark's excellent publications I have concentrated first printing through Photoshop and the Epson printer interface rather than using QTR.  I have prepared an icc file for Epson Archival Matt paper using QTRICC-RGB and the Gray Scale 21 step file.  My actual photo files originate either as Camera Raw or RGB tiff files from VueScan.

Questions:

 When do you use QTRICC-RGB and when do you use QTRICC?  Why?

 If I'm using Photoshop/Epson to print why not use RGB file rather than convert to a Gray Scale file?  Won't I have more information in the RGB file?  Will I get better prints?  If not why not?

Thanks one and all for your kind help.