pwm or gpio for pled display on beagle bone?
It would help if you gave a link to the part.  Often, these have a predetermined bus type like SPI by which the device is intended to be controlled.  If you use GPIO to do this, you could certainly bit-bang it, but you might be better off looking at how to implement the appropriate protocol using the built in Beaglebone features.

PWM is a different beast.  It might be useful for controlling the backlight of the display.  I haven't seen such displays actually controlled by PWM before -- but again, if you post the part, I can be more specific.