This is also an interesting question because the answer on the face of it is that with nonduality there is no “out there” as opposed to “in here” because that is a duality, and nonduality attempts to get at what is there prior to the dualistic split, i.e. suchness. But the part of the question that asks about it “existing separate from the world” brings into play what Heidegger calls Dasein, i.e. the kind of existing thing whose ecstasy projects the world within which it finds itself (Discoveredness, Befindlichkeit, i.e. we discover ourselves already within the world that it turns out we project a priori, the projection of that illusion we call Being, which is really a doubled illusion that acts as a reflective mirror, rather than merely what is found, i.e. this and that. Being in our tradition supports the essence of the things “whatness” with a substrate or substance through which things can be the same, though difference, i.e. Tropes operate through it like Metaphor, Metonymy, etc. For Heidegger the world exists though our ecstasy by which we project it temporally as a space in which we can dwell, and BE. And in that space we can experience the process of Becoming. But if we did not have the Parmedian idea of Being as Stasis, (Pure Being) then we could not experience the flow of Heraclitian fire, i.e. change changing everything always. In this it is really only Knowledge that is perdurant but in the Indo-European tradition we project perdurence on things which may also be done by others but not in the unique, strange and onefold way that Indo-Europeans do. Now if we ask what is the distinction between Static Pure Being and Dynamic Process Becoming, since Being is the highest concept, these either have to be mutually exclusive, i.e. something we are dogmatic about, or as Heidegger suggests they may be equi-primordial, in which case Being has kinds, and as such because it is the highest concept, then there must be a third kind of Being (as Plato called it in the Timaeus) which gives this distinction itself a kind of Being. Merleau-Ponty calls that Hyper Being (Derrida calls it Differance [differing, deferring]; Heidegger calls it Being crossed out). And Merleau-Ponty points out that it has an opposite which he calls Wild (Savage) Being using a term from structuralism already overloaded by Levi-Strauss. If we realize that the kinds of Being are meta-levels in the Theory of Higher Logical Types then that is half the battle because then we realize that the difference between the kinds of Being is the greatest that can exist in the world. In essence when we see the four kinds of Being together (not taking into account the singularity of Ultra Being) then we have a vision of a face of the World which we normally only see clearly in an emergent event, where the baseline of Nihilism is reset. Now all that is entailed, in my view, by the projection of the World in which it finds itself by Dasein.
As we explored earlier All this is implicit in the relation between Parmenides Ways and Heraclitian Fire, which Plato calls the Greater and Lesser initiations. The third kind of Being (Hyper Being) is the difference that makes a difference (Bateson) between these two kinds of Being. As such it is a slippery and mercurial kind of Being always introducing differing and deferring of DifferAnce into the play of the world (John S. Hans). But none of these standings through Being are Existence proper in the sense of nondual emptiness (Buddhist) or void (Taoist). At the fifth Meta-level of Being there is both Ultra Being as singularity and emptiness/Void (Striated/Unstriated). It took me a long time to figure out how Ultra Being could exist, but basically if ou have two different types of interpretations of existence then Ultra Being is the difference that makes a difference between them. This is so interesting because it points the way toward the role that Being plays. We see it externally as a singularity in existence but inside it is differentiated into meta-levels fo maximal emergent difference. It is the singular distinction between two different interpretations of nonduality. Duality unfolds from this singular distinction between interpretations of nondual existence. If we remember that illusion exists in existence as well, and that Being is really just a doubling which makes illusion reflexive, then we realize that existence itself is the difference between these two layers of illusion. So from the point of view of Being, it is a distinction between interpretations of Existence, while Existence is really a distinction between two layers of illusion, i.e. illusion folded back on itself, i.e. illusory Illusion. In this way we can see that Existence and Being are completely intertwined each distinguishing the other.
When you realize that there is this deep intertwining of Being and Existence, i.e. neither can really be completely what they are without the other, then you actually see that the doubling of illusion into Maya is actually progress in our understanding because Existence becomes the difference between the veils of illusion. And likewise without Ultra Being as a singularity you cannot distinguish between different sorts of nondual interpretations of Existence. And it is this kind of deeper realization that I think Tantra of the Tibetans comes out of, which on the face of it looks like a falling back into the illusion of Being, but instead leads to the formulation of DzogChen by Manjushrimitra where he applies the logic of Nagarjuna to Buddhism itself and sees the two truths as nihilistic extremes. Buddhism itself was a heresy within the Hindu strain of the Indo-European worldview that revolted against the idea of Being, and instead saw existence as the flux of aggregates. But once you get into existence, then you realize that in order to get to deeper levels of understanding of existence you have to bring back Being, because otherwise you cannot put Buddhist Emptiness in the same poem as Taoist void as Stonehouse does, i.e. you cannot actually get the best our of both Buddhism and Taoism (Bon) which are actually different but you cannot tell that difference without bringing another kind of existence which is Maya, Dukah, Dunya as seen from the outside as a singularity.
So we see that there are two views of Being, i.e. from the point of view of existence (from the outside) and from the point of view of Being itself, i.e. from the inside. In the one case we see a singularity, in the other case we see the fragmentation of the kinds of Being. So there is an inside and outside with respect to Being, but not Existence. Existence is Unary. And Existence can be interpreted as Nondual, eiher as emptiness or void. To make that distinction we need the singularity of Ultra Being as the difference that makes a difference between different interpretations of the nondual state of existence. So if we take the world to be a schema projected by Being then there is some sense in which existence is out there beyond the world. But that leaves us to quibble over the word separate. The non-dual lacks the following characteristics: Separate, Fused, Separate And Fused, Neither Separate nor Fused. It is something else beyond these four logical states. It is Not One! Not Two! So the fact that there are two interpretations for Existence without illusion as nondual is itself a problem, because that calls for a third the singularity of external Being, i.e. Ultra Being. What this indicates is that there is actually multiple levels of non-duality and that Emptiness/Void as Striated and Unstriated terms in the Pleroma, are not the ultimate type of Nonduality but there are deeper froms of nonduality. I call these deeper forms of Nonduality: Manifestation, using a term from Henry’s Essence of Manifestation which he attributes to Meister Eckhart.
We know now from Heidegger that there are striated and unstriated Being/Beyng in the Pleroma as well as their opposites Forgetfuness/Oblivion. To the extent that nonduality is reflected in the Pleroma then it appears also as Striated and Unstriated as Emptiness/Void. So that means that there is a standing beyond the Pleroma where nonduality is not made dual, i.e. which we are calling manifestation. Now the Pleroma is the field out of which the Worldview arises, and clearly the Pleroma arises from this deeper nonduality of Manifestation. So there is a sense in which Non-duality is “out there” beyond the world, if we take it as being always already prior to the arising of the pleroma and world. But as for being either fused or separate we must apply the tetralemma to that even at the level of Emptiness and Void the two canonical interpretations of Existence.
So from one perspective the answer to your question is true, instead of false, with some caveats, like separate/fused has no meaning either at the fifth standing (Existence) or beyond that at the sixth standing (Manifestation). In some sense these distinctions are only apparent, they are standings we take toward what we find (existence), or if we enter into reflexive illusion (being), or if we see nonduality without differentiating interpretations of illusionless existence (manifestation). “Standings toward . . .” are our own embodied standing.
I hope this is sufficiently bewildering . . .