People have been complaining that Kobo's screen is too dark but it looks like PocketBook has a darker screen than Kobo.
https://imgur.com/gallery/WMFc8Sm
I need to increase PocketBook brighter by about 20% to match Kobo's brightness. At a certain point when Kobo becomes comfortable to read, PocketBook displays visible blue light.
Edit: PocketBook flush screen is not working out well. There is a noticeable irregularity on the right side of the screen when you turn on the brightness whereas Kobo's light is even throughout the screen.
Thoughts about the screens?
I find it best not to compare eReader to eReader and to read for some time on each one separately and then make your conclusion.
On Color Settings
Unlike, Kobo, PocketBook allows you to change the color settings to your liking. It took me some time to figure out how to do that because this option is not available when you go into appearance settings (fonts and margins).
This is a strange and unintuitive choice of the UI but to change the color settings, you have to click on the actual image in the epub then zoom in and then you will get the color settings at the top right corner. Once you change the settings, you will have the option to save them and apply to this ePub or to all ePubs in the future.