USB type-C ports max power supply from MacBook Pro?
USB-C alone allows 4.5 Watts ( 900 mA @ 5 V ) and thunderbolt 3 improves on that greatly. 

According to Apple:


  MacBook Pro (15-inch, Late 2016) and MacBook (13-inch, Late 2016, Four
  Thunderbolt 3 Ports) can power two devices that use up to 15 watts,
  and two more devices that use up to 7.5 watts. It doesn't matter which
  side of your MacBook Pro that they're connected to—power is delivered
  on a first-come, first-served basis.
  
  MacBook Pro (13-inch, 2016, Two Thunderbolt 3 Ports) can power one
  device that uses up to 15 watts and one device that uses up to 7.5
  watts.


Thunderbolt Source: https://support.apple.com/en-us/HT207256
USB Source: https://support.apple.com/en-us/HT201163

The above specs are the same for the 2017 MacBook Pro models. The MacBook models only have USB levels of power and data available.