So you know how greyish is the background on Pearl Eink (On day light it' is already very dark then at night a strong light is needed). There is no light on big Eink screen I read. So it will have to be an external.
My advice was to wait for E Carta bigger screen cause it is easier to read on low light (and will keep his value longer). It'is coming:
https://www.mobileread.com/forums/sh...d.php?t=275632
No idea how Pixel Qi display work. If it support mouse pointer, connect to windows and you can have it for 100 it's good beside the low resolution and 16/9 ratio.