Without going into too much detail (because the subtleties and variations really are a bit more complex), as a broad generalization, people characterize the spiritual goals of Right Hand Path and Left Hand Path in fairly diametrically opposite fashions. The Right Hand Path tends to get characterized not just by the control of things like desires and pleasures, and service to “the greater good”, but by the mystical goal of “union with the divine”, sometimes characterized as annihilation in God, or other forms of transcendent extinction. The Left Hand Path tends to get characterized not just by the acceptance and even indulgence of desire and pleasure, but by the development and ultimate realization of the individual self in godhood. The Right Hand Path involves union, the Left Hand Path involves (at some level at least) the fulfilment of separation and separate existence, though I would personally modify that terminology on the basis of the distinction between separation and individualization, and union and relationship*.
From my point of view, it is really not quite as simple or polarized as sometimes presented. However you want to envisage the Greater (or transcendent) Whole with which we supposedly achieve ultimate union (according to much orthodox mysticism), it seems clear to me that we actually are already one with it, but without loss of individualization. We might not be aware of it, but it is so. Of course, I do not believe in a “creator God” myself, but whatever it is which is referred to here, we are in a sense already part of it, albeit individualized, and capable of self-realization. I could never see why we would come from something, only to disappear back into it. There are all kinds of stories about God gaining experience in separation and multiplicity, but the most consistent of them that I am aware of make us the conscious ones, not “God”. But really, why go through this just to go back again. It is all stories, but the more abstract they become, the more childish they sound to me. Yet there is a greater whole which we can find connection with, and benefit from, and find our place within (just not a pre-ordained or subsumed one). There is relationship. But it does not abrogate our individuality or our freedom, far from it.
Which brings me to the goal of Left Hand Path “mysticism”, which is the realization and liberation of the self. Here there are few stories, because rather than stories, there is life, and moreover the life that you, and only you, can create.
My suspicion is that in the reality of mysticism and magick (rather than our definitions and thought structures around these things), there is only one basic thing, with immense freedom as to what the individualized consciousness does with it. It is not that “all paths lead to the same goal”, in the rather facile, greetings card way that is usually presented. But I suspect that anyone who has actually realized a truly deep mystical goal has got there by straying from every path except their own, whether their “tradition” allowed it or not.
* this might seem a bit academic, but I like words to have emotional as well as rational resonance.