I'm fully in the reMarkable camp - bought both generations as pre-orders, both still seeing regular use (one as my work note device, the other as an around-the-house note device). I'm very happy with them, I've enjoyed watching the software and features evolve and grow over the years, and I'll likely be unable to resist pre-ordering an eventual third generation device (if it has a colour screen, I won't even).
So, with that in mind: I wouldn't recommend the reMarkable if a core part of the usage is reading ebooks. It's a phenomenal note-taking device, but the reading experience needs considerable work. Don't get me wrong, the software is night and day from where it was, particularly with the major improvements with PDFs, it's just that it's still not designed for ebook reading as part of the core user journey.
The most recent reddit thread I can find, if you want opinions.
Some of the alternatives, should you want to research: supernote, boox, kindle scribe. Try and find comparison videos are articles against the reMarkable, as it's still widely considered a market leader (and, I think, remains unmatched when it comes to pen latency).
As you're already in the kindle ecosystem, the kindle scribe may be the best fit for you. However, be sure to try and find recent reviews and comments - the release excitement was quickly dampened as people discovered that the software was essentially a kindle with the barest of basic writing functionality.
What's your budget (all of the above start ~£/€/$350)?
What features are most important to you?
What's your desired workflow?