It sounds like what your describing is typical of how people are when they first take vicodin. I mean its usually where people say like they can't explain it, they just feel okay, they're not upset, nothing is on their mind really, they're just at peace with the world and just simply feel absolutely fine.
from what you've said so far, I think it is composed of myrrh. Myrrh provided me the typical virgin vicodin experience, which is something I haven't felt in many many many years, so I was stoked.
It also sounds like it could have benzo action, the benzo action is typical of the tranquility, but benzo tranqulity is that you don't care, and kinda like apathetic but satisfied, opiod tranquility is more like a blissful peacefulness where you will prolly just nod off any questions and say oh im feel perfect, nothing in the world bothers me, and its like your very happy and tranquility.
And I say benzo possibilities only for a long shot, as very few people react to benzo's like this, I do, my mother does, and I haven't met anyone else - but I have a reverse reaction to benzo's, by reverse I mean I don't have a typical reaction, benzo's give me the munchies like none other. benzo's make my nausea go away, and when I take em they tend to cause me to want to stay awake or be more active.
And being this is said to be plant like, and not a typical tranquil or typical euphoria, I think its possible to be like myrrh and mulungu - both are atypical for their class.
myrrh, mulungu, sounds like a good combo to me. Also, you said it had a unique taste, myrrh imo is one of the absolute best tasting smokes you could ever bubble in a little bowl. I love watching myrrh terpenes just bubble and contort while u light it.