Charging devices with different max voltages
If you are using a USB 2.x connector then you should supply only 5 V.
Configuration of the D+/D- lines can advise of the peripheral charging current required. If you don't use these lines then you will simply provide the current defined by the peripheral. 

If you are using a USB 3.x connector then you can negotiate the output voltage based on the connected peripheral device. 

This answer provides a starting point for your research. Short answer.... read the USB 3 spec.