It seems like it is based on a combination of an earlier draft of the novel and the translator’s own ideas, because it contains things that were in Stoker’s notes but not in the final manuscript, and a lot of Scandinavian mythology is added. It is more overtly erotic and political as well.
More overtly erotic? How is that possible, unless there’s a sex scene?
Adding to OPs note:
In Makt Myrkranna, Dracula comes to England not alone, but rather with a deaf-dumb woman who is apparently his slave and together with another beautiful aristocratic female vampire, Josephine, who flaunts her sexuality.[20] Josephine is described as having her “neck and upper chest revealed” while wearing a “necklace of glittering diamonds”, whom Harker finds “something indecent” about, despite his evident attraction to her.
So is there an English version of the Icelandic version?
There is indeed! It’s one of the things that makes this such a humourous story
Edit: https://archive.org/details/powersofdarkness0000vald Here it is! Enjoy (even if one’s enjoyment is just in knowing that this exists)