Why are both a USB 2.0 cable and a USB 3.0 cable provided with my Cintiq 27QHD? Which should I use?

Normally the USB 3.0 cable should be used to connect Cintiq to the host computer.

Some computers and USB 3.0 hubs generate interference which can reduce the operating distance of the ExpressKey Remote. If necessary, increase the operating distance of the ExpressKey Remote by using the provided USB 2.0 cable adaptor. Please note that using the USB 2.0 cable adaptor will cause the USB 3.0 ports on the Cintiq 27QHD to operate at USB 2.0 speed.

Note that the normal Cintiq functions are unaffected no matter which cable you use. Only the speed of the USB 3.0 ports are impacted.