Drawing is very good in my experience, though I haven't tried the reMarkable or the Kobo Ellipsa. Maybe I just got used to it really quickly but it doesn't lag enough for me to actually notice when I'm writing on it, and hasn't slowed down at all since I got it.
Here's the link I followed to set up cloud sync for reading positions/notes/bookmarks:
https://raymondlamsk.blogspot.com/2018/03/moon-reader-how-to...
Calibre is a very useful piece of software regardless of what ereader you end up with, and there's this feature request about syncing back to calibre too but I haven't personally explored it. https://github.com/koreader/koreader/issues/3814
One annoying thing I sometimes run into is that if you keep wifi off, you'll have to remember to turn it to sync. But that's understandable.
And how is boox. I've been looking for an ereader with a very big screen and haven't found a decent one yet, but the boox might be the one. Is the drawing any good?