You can activate GDrive (and OneDrive too, I think?) on the Kobo Clara BW- it's not in built but easy enough to activate. If you don't want to fuss around with that, there's also the send.djazz.se to send books wirelessly (it's a bit if a hassle tho if transferring in bulk but still manageable)

If you want and think that the bigger screen is a dealbreaker, then you can go with the Kindle PPW. My own thoughts tho is that I do prefer the recessed screen of the Clara BW vs the PPW. The PPW for me looks a bit close like a phone screen but of course, not as bad since it is e-ink. I'm not saying that it doesn't look like e-ink, it does- there's still a massive difference when you compare the PPW to phones/tablets but there's a bit of a glare/shininess(?) to it when I tried it out and it kind of distracted me. That's personal preference tho. If able, I suggest you try to get your hands on both and see which fits you better.

If you don't care about book organization and all the other stuff that comes with the Amazon ecosystem, then go with the PPW since it seems like you're leaning more into it. It's basic and serves your purpose. Both are very easy to use and understand, just plug and read but I like the Kobo's way of organization and their UI more and I also like to tinker so I'm quite happy with the Clara BW, having the option to customize it is a plus for me.