Magic is the ability to persuade the Multiverse to look the other way for a while. Strong magic is the ability to tell it to look the other way very persuasively, and keep it distracted so it doesn't notice.
Demon magic at the level of the Varga is the ability to
order it to not only look the other way, but
forget that things were ever different.
And make it stick
Varga created matter, even if the rules of the reality strand in question would normally disallow it, works as designed. Even something as ridiculous as EDM. So moving it around isn't that much problem, it's not going to spontaneously go stale or anything.
Much the same is the case of the fractal dimensional techniques. What they create is stable, unless either designed to be unstable, or deliberately dismantled. They're essentially completely self-contained knots of spacetime that just
are.
On another note, one can assume fairly plausibly that if you manage to end up in a universe where the physical constants are sufficiently different that most of your technology won't work, you don't really care, since they'll by definition be different enough that
you won't work. If you've modified physical rules enough to make electricity not flow right, normal biological life is screwed...
Unless you have The Amy on your side, of course