I'm going to agree with FrustratedReader on the fitness of eInk screens for WYSIWYG editing. I've never tried an Android eInk reader (like the Onyx Boox Nova Pro or the Boyue Likebook Mars) but my experience using eInk web browsers tells me that writing on an eInk device would probably be a frustrating experience. But if you do get an Android eReader I also agree with FrustratedReader that an OTG cable and a Logitech (or other brand) wireless keyboard would be a better option than a Bluetooth one. You can also use both a mouse and a keyboard on the same USB adapter.
I've played around with screenwriting software quite a bit, including trying out WriterDuet. If it were me I would go at this from a different angle. I'd use the Fountain syntax (
https://fountain.io/) and an Alphasmart Neo keyboard (
https://www.ebay.com/itm/Used-Renais...ty!83646!US!-1) — this is just one seller, lots of them on eBay — and then import the Fountain formatted text into WriterDuet. Or you could even read it into 'afterwriting's (
https://afterwriting.com/) Fountain editor (online, or it can be downloaded for offline work) and save to FDX format and read that into WriterDuet. The advantage of the Alphasmart Neo and Fountain format is that you could do the bulk of your creative writing in a non-LCD screen device and just do your editing in computer or tablet (Neos can connect to tablets via an OTG cable as well).
At any rate, for what it's worth.
EDIT: Meant to add, Alphasmart Neos last about 700 hours on 3 AA batteries.