If you save B/W only then the printer will only use the Black Cartridge.
On other occasions it may (depending on Printer) use the coloured inks to 'create' black.
Also Different papers DO affect print quality esp. with Photographs.
If you want the best result you should try and use Manufacturers own paper which has been made and rested on their machines. Obviously you pay a premium so it's only worth it for special Photos.