Memory in pixel means that each pixel remembers its current state, saving on a lot of power budget because the bus/LCD controller is completely shut down, it essentially only uses power to update the display. Versus a traditional LCD or oled where you need to send it data at x refresh rate continously, meaning the high power draw bus and controller are constantly slurping power.

Even though eink has gotten better I still wouldn't use it for something like this, the refresh rate is still a tad too slow, the controllers are always proprietary weirdness with crazy voltage waveform magic to clear the display properly, resulting in that ugly multiple flashing that most eink/epaper displays do.