It has been said that words bind the boundless. One way in which that is true: Many traditions point to the same truth and have practices that lead to the direct experience of it. Words spring from the context of particular orientations and traditions and are flavored by those perspectives. But, strip away the trappings and the horse underneath is the same.
As Buddhism and Hinduism continued to be practiced over hundreds of years, the description of the actual experience of stages of the path and ultimate direct perceptions of truth became almost indistinguishable.
In my limited personal experience, I can relate to the experience of unity over the years. But, when I started having the experience of "no-self", it was quite different from an expanding sense of unity. With unity, everything seemed to still be in terms of the self, "I am all that I see, hear, touch." When I began to experience the absence of self, things were no longer in terms of this "I". Also, this subtle sense of duality that remained linking "I am" with "all that I perceive" dropped off. It shifted from being "I" centered to not having a center, from seeing the world in terms of the self to all things equally participating in ubiquitous awareness, all things acting and reacting in perfect accord with all other things. Life just flows. And when I am not directly currently experiencing this, there is an indelible sense of it that never completely leaves, a fragrance of unity that can never be forgotten.
On the other hand, when someone steps on my toe I still want them to get off. I can still be self-serving at times - sometimes surprisingly so. But, there is no dichotomy or paradox in that. I still have the desire of "self-"preservation, i.e., I prefer to continue living rather than walking in front of a bus. But, if I look for a separate self, none can be found.
Yet, there is a remainder or residue of ignorance. There is always more to unfold. The depth is unfathomable and as such, no end to the limits of experience. We are not omniscient, all knowing, concurrently experiencing all things simultaneously. We are still in these bodies and perceive through these senses, which tend to give a sense of localization and hence a sense of separateness, "I hear the sound coming from over there." Yet, what is more prominent than this sense of localization that separates or differentiates is that there is no "out there." All things appear and disappear in awareness itself. Nothing is outside of awareness. Because of this, there is no sense of separation but also no tangible sense of self. It's not that there is no sense of self what-so-ever as it is that it is no longer prominent and no longer calling the shots. The awareness shifts from what is good for me to what is good for the planet. It shifts from my suffering to the human condition we are all in. It shifts from seeing someone like Trump as inherently greedy and self-serving to seeing the light within him and how it is obstructed by his misperceptions revolving around his strongly solidified sense of self and self-importance, for example.
One problem that can occur if someone begins to think that they are everything, completely unified with God and the universe, is that they can take on an identity of being a savior or avatar, that they are on a mission to save others and are therefore above others. They allow themselves to play that role and welcome or even encourage others to participate, even to the point of guru worship or worship as a divine incarnation. I find this very problematic, both for their own complete liberation and for those that are disciples. There are many examples of charismatic figures that have taken on this identification with an exalted level of personhood that is itself a form of division and separation. Buddha addressed this with the medicine he called "Anatman" or "No Self". To this day, Theravada and Zen Buddhists emphasize that there is no self to be separate as a cure for this delusion. When spiritual awakening is more mature, there is no sense of anything special about oneself. Everything is completely natural. There is no need to set oneself up on a dias to be revered. Awakening is no different from bamboo, ocean waves, a smile, or taking a dump. No need to exalt when everything is exalted by its very nature.