>Boox Note Pro< for now a recommendation!, Why you may ask?...
I'm using the last system-update (2019-12-31_13-31_2.2.2_1843383) an have now a very good experience, it's stable and the UI is intuitive (way better build in notes app, app optimization for external android apps now integrated)
PDF:
I use "Xodo PDF Reader & Editor v4.3.8" (the bookmark-Button is there even when not quit visible ;-) ...other versions don't show the menu at all and I like it quite more then the one Onyx provides. It's also a seamless experience on your android phone when it comes to annotations. The marked files are also working 100% with other readers like Adobe, XChange...on PC. (Foxit Business v6.6.1.apk is also possible, but doesn't have split screen built in)
ebooks / epub:
I like annotation as you may have figured out, therefore i use "Moon+ Reader Pro" v4.5.7 / I can export the annotations ("share" then export a file) and I use my own Cloud App (Synology Android App works too on Boox) to sync the file ...and the book to my phone.
Therefore I have my latest books with reading position and with all the annotations always with me even when I don't carry my boox note pro with me, and if I destroy/lose/get my Boox stolen from me all the data is in >my< own Cloud / Synology Diskstation.
...now the reader works for me
Hope this helps anybody with similar requirements.
