@Burning_Full_Fingers
Well there's the Tiering System page this platform uses for reference.
As far as I know, 2-A is as said here:
2-A: Multiverse level+
Characters or objects that are capable of significantly affecting,[1] creating and/or destroying a countably infinite number of separate space-time continuum.
But as far as I've seen, including one statement I remember Le Fay said about "parallel universes" (although I can't remember if she meant like the mythos realms where the Gods and stuff live at or something else as she mentioned this alongside Norse's Yggdrissel), everything else fits for a 2-C scale cosmology the verse works.
2-C: Low Multiverse level
Characters or objects that can significantly affect,[1] create and/or destroy small multiverses which can be comprised of several separate space-time continuums ranging anywhere from two to a thousand, or equivalents.
Everything from parallel dimensions, alternate timelines, parallel worlds separate from DxD like Denpachi and OG Slash-Dog (not the Fallen God Slash-Dog story, mind you), Melvazoa being able to manipulate parallel versions of himself, etc. all fits for this.
2-B is for 1001 to countless worlds, which DxD wouldn't apply either.
Altogether, the entirety of Ishibumi's works is plentiful but I think they'd still be on lower end of 2-C.
The Dimensional Gap/Void thing would be another matter in relation to all of this.