[Quoth]

You want an LCD Tablet like a 10" Lenovo for colour. Inherently colour for eink will either be dark, needing massive front lighting (Triton) or washed out (Kalido). Physics limits of eink approach, not technology. You'd need an as yet non-existent technology for passive colour as good as printed paper.
Larger than 8" is very expensive.
These are not a new market segment.
It depends on the Android app as to how well it works on eink.
The Boyue Likebook Mars is only 7.8", but it's nearly as big as a Forma and about €45 cheaper with 3.5mm jack audio, sd-card slot, BT for audio, BT for a real keyboard and Playstore that can be turned off. Koreader APK worked by direct download. Most Android Apps only need the Google Framework on to install from the Playstore. The Native PDF reader does autocrop and background/watermark fixing, but the built in epub reader is inferior to koreader.
I need the 10" LCD tablet (nearly 1/2 the price of a Mars) for colour or for technical PDFs. I use Xodo on it for PDFs and images and Lithium on it for epubs, but the Mars is superior for smaller PDFs.
The Kobo Libra is best to annotate ebooks, but I read Gutenberg and other PD ebooks on the Mars as koreader allows fixup of format. You can install koreader on a Kobo, but I've never bothered. I use Calibre to fix up any important Kindle or epub ebooks.

I've not used A4 paper and a pencil for years. Decent laptop since 2002 (replaced late 2016) and a 2nd PC + screen in the workshop. Mostly stopped printing PDFs when I got the 10" tablet, but I might print old service sheets for workbench to annotate with pen & highlighter when restoring / repairing vintage electronics.

I stopped printing manuscripts for proofing when I first got an eink Kindle.