Digital BW, The Print

I just started using a C84 with EZN inks and am really pleased with the 
initial results!  Finally, I have inkjet B&W that I would be proud to 
hang on my wall. My thanks go out to all of you who have contributed 
answers on this forum (and particularly to the seemingly tireless 
Clayton Jones)! But, of course now I have some questions that might 
help my understanding and work flow:

If an image is grayscale mode in photoshop, will it print 'black only' 
on a C84 even if BO is not selected on the printer driver?  

Does a B&W image have to be in RGB in order to use all four inks?

Thanks,
David