Each light string is powered by a bank of 4 AA batteries running at 6 volts plugged directly into the string and the Pixelblaze controller. There is no on/off switch in the circuit because that adds time, expense and complications to the build. Also if there is an on/off switch it will get bumped during a performance or add confusion in troubleshooting when time is short.
The Pixelblaze can run off a USB power bank but not provide full brightness through the USB connector. The usb connector is also prone to being unplugged or damaging if flexed the wrong way. The other consideration is either trying to charge a dozen power banks, or trusting each band member to charge them before the show.
I went with 4xAAA 6v because the controller and the particular string of lights I chose can be powered off the same bus. At full brightness the batteries get a little warm. At 33% they can run for several hours and are plenty bright.