Speaking from friends opinions, reMarkable tablet is the way to go for folx often working with PDFs. Great annotation and highlighting. E-ink display. https://remarkable.com/store/remarkable
I wouldn't recommend this. PDF support is horrible, particularly if you have a two column layout file. You cannot correctly zoom in far enough in most cases - in the sense that zoom is possible, just absolutely impractical. Without that, you generally need a magnifying glass to read the text on the display.
Very nice hardware, just awful software.
Are you talking about the new version or the old one?
Version 1. But as I say, the hardware is good. Version 2 will have even better hardware specs, but the operating system I suspect will be the same.
Aren't most books single column layout though? If I have to read a paper I can use a tool such as k2pdfopt[1] and read it on my Kindle.