Mokou asked me to send this.
“Okay, last proxied response for real this time.
Ogbunabali seems confused on exactly what an Otherworld is; it's not a single location, but rather an umbrella term for anything that exists outside the Earth and Moon. The Netherworld, Hell, and every other cosmologically significant location is an Otherworld.
With that out of the way, let's get into the Dream World itself. First off, the Dream World doesn't scale
solely to the Netherworld or just any one Otherworld; rather it is superior to the
entire cosmology (minus itself and the memory layer).
It's even been shown to recreate the outside world, which is where the existence of the 10D brane cosmology was proven to begin with, and even this is just an infinitely small part of the Dream World as a whole.
This panel from chapter 29 of WaHH demonstrates that there is a layer of reality-fiction transcendence between the Dream World and the physical layer, as the Dream World is superior to the extent that it 'controls' the physical layer. Since the physical layer is quite blatantly 10D, this makes the Dream World 11D by default. That, and the Dream World contains recreations of the entire cosmology within itself, as demonstrated in
chapter 33 of CoLA where its stated that "the Dream World and reality are two sides of the same coin".
Onto the scaling, I've always been iffy about scaling Doremy to H1-C based on her residence being within the Dream World. However, her ability allows her to create and destroy dreams, as well as utilize them in combat, and dreams are
repeatedly stated to be equal to reality. Therefore, whenever a dream is created or destroyed, it is in fact creating or destroying a 10D 'reality' along with it. So scaling everyone to H1-C off of Doremy is still valid (Yukari also has a dream creation feat of her own).
We of course also have the primordial gods, who scale to the entire cosmology by virtue of creating it. We also have numerous statements that Yukari's ability is
comparable to said gods and
can fundamentally undermine all of reality, scaling her to the entire cosmology as well. Reimu should arguably get this scaling as well, as
Okina heavily implies her ability is similar to Yukari's.
TL;DR: The Dream World does in fact exist 'above' the physical layer in a qualitatively superior fashion, H1-C scaling is still valid, and if the memory layer is still 1-B via existing above the Dream World, then primordial gods should be 1-B, and Yukari and Reimu would be 1-B via hax.
Also @Mobi2 I'm pretty sure the geography of Gensokyo sections in SCoOW are non-canon and just speculative, but the Netherworld is an Otherworld regardless.
Take care everyone. I hope I won't have to keep making proxy responses, but hopefully this clears up a lot of confusion.”