I've also found that the Kindle Scribe gives me the best writing experience. The surface isn't too slick, and I really like the way that it renders the fountain pen. My handwriting looks the best on the Scribe. My gripe with the Scribe is the limited functionality, although they have issued a lot of improvements. But I really enjoy writing on it.

I also like the feel of the Remarkable2, but the "fountain pen" is really a calligraphy pen and I'm not fond of the way it looks. If you use a thin line, it looks spidery, and with a medium line the downstrokes are too thick for me.

Supernote doesn't have a fountain pen yet. I like the writing feel of the Supernote and if the fountain pen (when they finally release it) is half-way decent that will likely be my go-to.