Searching for b&w e-reader recommendations

I've been reading on a 10-inch OLED tablet for over a year now and I'm starting to want something better for my eyes.

Likely prefer something on the larger end, 7" or higher. Mid-range sort of budget, no more than four or five hundred. Do not care for ecosystem, books will be sideloaded, typically epubs but am savvy enough to manage conversions with Calibre if necessary. Ability to read manga (.cbz) would be a positive but not a must.

Is there a big difference in quality between the Carta HD, Plus, 1200, 1300 screens?

All advice and recommendations highly appreciated, thank you.