From my own experience, especially when using 5-MeO-DMT, I always interpreted it to be a semantic difference, perhaps leaning a bit towards No Self being a more accurate description of the raw reality. The further you slide into it, the more your sense of individuality is diminished. But I can also see how that all-encompassing empty perception could itself be called the True Self.
If there is a meaningful distinction between the two in practice, I'm not advanced enough to perceive it. When you go deep, it feels as if both are an acceptable description.
I've had precisely one 5-MeO-DMT experience, so I may not deserve a seat at the table, but I have had a couple experiences that pertain to this.
Most relevantly, I had a breakthrough on the 5-MeO-DMT where it felt like dissolving into the ocean of everything. So my initial thought would have been that it felt like "No Self" as the part of me that held onto my identity was offline and the division between myself and everything else faded. That was especially true during the initial part of the journey were "self" seemed to uncouple (my understanding is there is a decoupling or effectively the temporary shutting off of the default mode network that handles what makes you, you). That experience of raw reality is so overwhelming without those filters that it feels like you are everything and thus nothing to identify as "self." And yet, as I recollect I also had thoughts about things that were unique to me or that related to "me." Perhaps the "No Self" is due to the overwhelm of the complete rush of experiencing so much. However, after "I" dissolved into nothingness, at some point my thinking got very quiet and clear and I was one with everything in a very clear and beautiful way.
That felt like the True Self to me, or at least resonates with that phrase. It was me without the filters and quirks my DMN layers onto experience. Arguably the main difference was that past the chaos of being violently ripped out of our everyday consensual reality I was able to just
BE. With the added resonance and lack of chaos, I was able to be...whatever you want to call it.
Perhaps less-relevant, I had a psilocybin session which I think would have been enough for a breakthrough but my guide had me moving around eyes open for a bit, asking me questions, which is not my preference. However, it seemed to keep me online and engaged even as I became aware of the connectivity of things. I felt a sense of being a part of everything and a dissolution of boundaries between myself and everything even as I still had those. It was a different substance and very different experience, but there were some similarities. The everythingness was not so overwhelming and my identity did not dissolve into nothingness even if thinking back it quieted down a bit. That felt like me sans the things that usually make up me or define me as separate from everything else, while also being a new perspective.
My point is, arguably, in both cases I achieved a version of myself shed of certain lenses and distortions. With 5-MeO-DMT, it was just so much all at once that it felt like No Self until I accepted, dissolved into nothingness, and then hit the peak where it felt like what
feels to me more like what I would define as my "True Self" or how you might define your soul, for lack of a better word. The psilocybin felt like loosening of things and a more gentle-yet-intense awakening to that spiritual connection. 5-MeO-DMT felt like a destruction and a storm that then left you somewhere else in the aftermath. But there was a clear thought that, again, felt like True Self or a pure expression. It's a slight distinction, maybe to the point of not being anything at all. But even if no meaningful distinction between the two exists, if felt like hypothetically you and I could talk from that form of conscious as "Selves" that were taking in everything to the best of our abilities as biological humans. I may feel different with further experiences, but that's the best I can come up with to describe it at the moment.