I got rid of the reMarkable and do have an Elipsa.
I have an Android eInk (Boyue Likebook Mars) and just for reading it's massively inferior to the Kindle or Kobo.
I seems to me the only advantage of the Boox Note Air over the Elipsa is Android apps, and a 7″ to 8″ 300 dpi is maybe more use for that (Kobo, Kindle, Google, ADE, Libby, Pocketbook, Borrowbox ebook apps, chess, email etc). The audio seems worthless on my 7.8″ ereader, a phone is more use than a 10.2″ or any eink for that and audio dramatically shortens eink charge run time, but with phone screen blanked the play time is good.
So simply looking at specs, comparing 8″ Sage, 10.3″ Elipsa and the Android eink Mars vs
https://shop.boox.com/products/noteair2
spec, I think a 7 to 8 inch Android if you need Android is better.
The Sage is best for epubs & notes of all the ereaders I have.