Herbert's own sequels, especially the first two, Messiah and Children, really seem to form, for me, the full story with Dune as part of the Paul story. I don't think they can be separated in Herbert's philosophical wanderings: Dune was about the creation and taking of power riding on the back of a religious movement, whereas Dune Messiah and Children of Dune are about the consequences of doing so. In these three, the ideas are really the main character, the world building second, and the story and people third. That is not to say the people characters are badly done--they certainly aren't, they grow, they breathe--but in my mind, the ideas and philosophy wins.
The later Herbert sequels were really more of "What if?" story telling once the universe was there, although ideas still have a solid role.
The Dune 2.0 books are really a different class of book and writing entirely. They are pretty much pure story: more than fan-fic, less (much less) that the original six.
But they DO address questions that lots of us over the years might have had. The first ones to come out, the "House" trilogy give us the back story of Leto and Jessica, Baron Harkonnen, Rhombur, the development of Ix, the court of Shaddam and the Princess Irulan. And, gift of gifts, Gurney Halleck.
The next trilogy, that you've read goes way, way back to the why they don't trust machines. I, too, found much of it way more bloody than I liked. The pre-Dune interested me, the rest, meh.
(Although in counter balance to the billions dying there, if you think about the implications of Paul's jihad later, there may be a similar toll--just not front and center. And certainly not "art."
I haven't read the "mid-prequel-trilogy" about the creation of the various important institutions--Bene Gesserit, etc. I did read "Paul of Dune", though, which filled in a time period in the first three of Frank Herbert's. It deals more explicitly with Paul's jihad. Overall, it was, well, ok, but not particularly memorable.
That may describe most of the BH & KA offerings: stories to fill in places our minds want to go, but clearly entertainment. Frank Herbert's volumes were about so much more. If you don't have Dune level expectations, they are an adequate visit with an old friend.