Will using a wallpowered usb cable to power a beaglebone black provide more power than on USB to computer?
The charger will have the USB connection configured so that the device should not think that there is a host on the other end. As for the rest, I cannot put it any better than Olin already has. But long story short, as long as there is 5V at at least 460mA plus additional current required by any capes and USB devices there will likely be no problem.