Re Character and role, particularly Protagonists -
I have heard Brian's criticism of Gaiman's MCs (I think Jo's particularly fond of decrying their lack of agency). I have also heard similar criticism of Epic Fantasy MCs. I would personally say that Gaiman's MCs are often ordinary people blown around by the winds of change, maybe lacking a little agency and finding it in the end, maybe not as loud and large as life as the supporting cast but easier for us to understand... and I'd say that for some Epic Fantasy too. And arguably Frodo and Bilbo are the most famous examples of such MCs.
And of course, there's plenty of scope in Gaiman's MCs. American Gods? Shadow is almost deliberately a blank slate. Richard from Neverwhere is the quintessence of what Brian is talking about. Charlie from Anansi Boys? I'd say he's fully drawn and active. Good Omens? Who the hell even is the MC there? And as for Morpheus himself, a more active and richly detailed MC in all of Fantasy is hard to find. Which just goes to show why I dislike doing this by author (another reason - Howard's Hour of the Dragon arguably veers towards the Tolkien-esque, while Tolkien's Smith of Wootton Major is pure Dunsanian to use the terminology in the OP). Books are in traditions (sometimes), authors hop around in them.
And to go back to Frodo... I think, stepping back and looking at it, you can see certain elements of the monomyth in Frodo. But he doesn't fit in with the sort of heroes made while looking at Campbell's work, and the type that are the most famous of the 70s-90s wave of Epic Fantasy that's most commonly held up as Tolkien-esque. To a certain extent, when people are saying Frodo isn't Campbell-ian, it's because the march of time has led to a certain type of hero being heavily identified as being like the Hero's Journey, to the point we maybe overlook others that aren't dissimilar because they're not what common parlance has as fitting in.
Now, to go back to the OP -
For me at least it is easier to think of these genre strands by descriptors rather than by names - trying to say "X is the source of Y" has too much luggage for me.
If we do that we get Saga/Epic - a large number of people experience events that shape the world, often in the shape of good vs evil; Adventure - a small number of people experience events that often change very little, frequently just for the hell of it; and... Fairytale/Myth? In which people encounter a strange world and lessons are learned? I find the "Dunsanian" the hardest to give a name to and what attributes I can give to it, mainly feel like Fantasy for the sake of Fantasy, the creation of new myth... and that is the very root of Fantasy.
So. I would suggest that if "Dunsanian" - Fairytale/Myth - should be held as the original strand of Fantasy, from which the Adventure Fantasy and the Epic Fantasy both spring - Adventure from American pulp writers, Epic from British writers steeped in medievalism. And I think you can see strains of Dunsany (who Howard described as one of his favourite poets) in both Howard and Tolkien; some of Howard's descriptions of ancient wonders (of which there's a fair few) have a certain similarity.
From there, I think you get further mutations and splits; trying to keep Fantasy into three main traditions is as trying to say all of Rock is either Rock, Metal, or Punk. I think Adventure splits fairly early into the "Ultimate Warrior" Conan style and the "Sharp Operator" style that more of Leiber, Wolfe, Moorcock and so on. There's a split between the more Good vs Evil Tolkien-esque Epic, and the grimmer "Stuff just happens" that you get with The Broken Sword and maybe even The Deep, that then leads into (to a certain extent) SoIaF and Malazan and Grimdark.
The interesting question to me is where you put all those Fantasy stories that are very deeply embedded in one particular community. Most of the books I've described so far are about wanderers (at least for the course of the book). But there's a big strain of Fantasy, which I guess you'd say starts with Gormenghast, that's about one particular group and society. Is that its own strain? Adventures? Or a mutation from the Epic? Or even the Fairy Tale? I found this interesting comment on whether Peake's books were fantasy:
"If your definition of fantasy requires wizards throwing fire, heroes questing for fairy-queens, then no. But if a vast castle encompassing bizarre peoples and ancient ritual can be considered 'fantastical', for their absurdity, their beauty, their dream-like reality of infinite age and significance... then put Gormenghast on the map between Earthsea and the Shire, just south of Anhk-Morpork."
To me... I guess they share that "Exploration of creation" type feeling with Dunsany when described thus. The manner of them is far distant on the spectrum though.
All I can say is the more I try to make sense of it, the more I am convinced that Fantasy has a very unruly family tree.
I did consider a whole new methodology last night/today - one built on where a book lies on four different spectrums; scale, morality vs amorality, action-heavy (i.e. fighting) vs light, and level of fantasy. And I do think you get some interesting results - Elric looks more similar to LotR than to Conan, because the scale and level of fantasy is closer - but it becomes obvious there's a lot of other measuring sticks that go missing with that.