Android OS version isn't that important for reading, and the latest devices shouldn't have issues for reading for many, many years. The batteries are more likely to go first. I can see why people get upset by Boox not upgrading older devices to new Android versions, but in practice it has very little effect on reading.
An example of manga on the Nova 2:
https://www.icloud.com/sharedalbum/#B0IGgZLKuGM5JIW
It looks great. All the screens of common modern readers are from the same company and share the same spec for their size. Boox has more user control over rendering than most.
Trying to match the screen to source resolution isn't the right approach IMO. For manga the source is typically 7", blowing it up to 10" isn't going to see any improvement unless you're doing it because your eyesight is poor.
If you do have good eyesight you'll notice the degradation in quality. 6/7/8" is fine for manga and will be 300DPI on a good device. On modern 10" readers the DPI is 227.
Many manga sources are poor quality, you'll enjoy them more on a 6". High quality sources will look great on 7/8".
I have a 13" Max 3 with the highest resolution e-ink screen, manga scanned at a high resolution looks terrible on it because the source physical size is so much smaller (but it's ideal for graphic novels).