I'm not sure there is much research into this area. I've been a member of the Native American Church for many years and the main things I've heard are things like a washed peyote is a weak peyote. What this means is that if you soak your peyote too long while cleaning them  you will notice some of the strength goes into the water that is being used to wash your peyote. The older the peyote the stronger it is. These are all things I have heard. Different localities may be able to self-pollinate while other localities may  not be able to self-pollinate. I wholeheartedly agree that it would be interesting to do sampling of tissues from various specimens and attempts made to breed for more potent specimens. Simply crossing specimens from the distant Northern regions and the Southern regions might prove interesting just to mix up the genetics a bit as well. Take specimens from the furthest western and eastern regions and breed those together. In 2 generations one could effectively breed the 4 most distant regional varieties together in effect creating a medicine wheel with ones crosses. Suffice it to say I don't know what effect that would have other than to be able to claim bragging rights for having done so. Still, it may prove interesting in other ways that have not perhaps been contemplated as well. One never knows what will happen until one does it.