I believe that entheogens are first and foremost about context and motives. The very same substance can be used for deep meaningful spiritual work... or for something completely different such as relieving boredom or self titillation. No judgment implies here and for each their own...
Psilocybin mushrooms
For me the most mystical entheogen is the psilocybin mushrooms. They also have a great healing power. Actually, thinking about it now I reach the conclusion that the mystical and healing aspects go hand in hand.
It is no coincidence that psylocibin is used for helping terminally ill people to deal with the fact of imminent death and the end of their physical life. The mushroom experience brings forth a dissolution of fear and a deep realization that this current moment of nowness is all there ever is ( what in Buddhist terms is referred to as 'timeless awareness' ). This creates peace, acceptance and profound healing.
However, I do question the possibility of integrating mystical experiences, beyond their immediate healing power. I found that my own too human brain lacks the translation machinery to take these cosmic experiences and bridge them into my daily life in a profound enough manner.
I am still to investigate this aspect further when my circumstances will allow it.
LSD
I find LSD to posses a great emotional healing power, in a somewhat similar fashion to shrooms. However it is not a teacher substance and does not have a distinct spirit/personality.
This 'lack of distinct personality' is actually what makes it unique and open ended for me. It does not shove anything in your face and it does leave it up to the user to give it a desired direction.
DMT and harmalas
DMT on its own makes no sense to me whatsoever. I really tried but it just don't

. I could never bring myself to vape more than 10mg before putting it away with revulsion. It feels to me like pouring pure psychedelic petroleum into my brain.
It's so fast and overwhelming that I end up concentrating on my breathing and wait for it to be over.
Combining dmt with extracted harmalas or other forms of rue/caapi in changa is a completely different story. I now have on my hands one of the most amazing shamanic, healing & spiritual, entheogens to work with.
The options are numerous. Different ratios of dmt:harmalas and different plant material will produce significantly different experiences:
Healing dominant, female spirit dominant, male spirit dominant, or gender-less. Alice in wonderland universes, future-techno worlds or the beating drums of the shaman's circle.
For me this is a vehicle for deep exploration into my own mind. A tool to face my most primordial fears and psychological biases.
For example I found out that what attracts me the most in it is the female presence and healing kind of experience, and it came as quite a shock to me as I was used to think about myself in very male oriented fashion... of being strong, self-sustaining, independent etc.
Quite a revelation it was which I am still in the process of coming to terms with.
And few words about Cannabis:
From my experience it can be used as a mild entheogen. However, for me it is very quick in habit forming, and this cancels out its possible use as an entheogen.
I do use it quite regularly ( few times a week ) as a sleeping aid mostly.