You may use Mevo and Boost power adapters interchangeably with no safety concerns. If you want to charge the Boost battery faster, you will want to use the Boost power adapter to do so. Our test shows you can charge Boost from 0% to 80% in 5 hours.
You may also use Apple's power adapter to charge both Mevo and Boost, but you won't get the fast charge time, and power may actually drain if you are charging the Boost while actively using Mevo (e.g. streaming).
Mevo's power adapter (as well as Apple's) provide standard USB battery charging at 5V/2A or 10W of power. Boost's power adapter uses Quick Charge 2.0 technology delivering 12V/1.5A or 18W of power. This makes it almost twice as fast as standard USB charging. Quick Charge is also compatible with standard USB devices; the power adapter checks the connected device and delivers the appropriate voltage/power.