I got the 32gig Paperwhite 4 only because that was the only way I could get the 3G version. I think I have about 100 books on it now. My older kindles have about 50 books each. I began to put a bunch of books on this since I have all that space just to see if I like it but I keep forgetting to put more books on it.
I keep my current book and a few books I think I might want to read in the near future and that's really all I care about having on board. My guess is that if I do get a lot of books on the Paperwhite it'll be hard to find anything and I'll end up taking most of them off. But who knows!
I have been piling books onto my 6 gig Nook Glowlight 3 so I'll have a lot of books in one place in case I end up without Wifi in a nursing home in the event that I get old. I'll probably keep doing that. I'm reading my current book on the Nook and the others aren't in the way but if I was looking for a next book it might be a small nightmare. Still, if i have no access to Wifi someday I'll welcome that nightmare.
Barry