Variations of Leto:
There doesn’t appear to be many distinct variations of Leto, which may have something to do with how little we know about her cult aside from its drop entwined nature with thst of her children. This may account for the lack of regional cult titles and epithets of the goddess.
Perhaps the biggest distinction in her cult is how she is treated in the mysteries. I have often commented thst the best way to understand the Hellenic mysteries is by seeing how the Hellenes discussed the subject largely through synthetic understanding of the gods with Egypt. It is in this light that I read the writing of Diodoros is when describing the mysteries via Egypt to have less to do with (in its very skewed perception) Egyptian religion but more as a direct dialogue of the mysteries without actually discussing them.
Here we are introduced to Apollon and Artemis as children of Demeter, and the role of Leto is that of a nurse to them, or perhaps given ghe strong narrative if Leto as their mother, perhaps foster mother would better describe it in terms of the mysteries. Here the influence of Leto’s domain and function with her children is the same, but in which the birth narrative of the twins on Delos is completely set aside.
I have considered this mystic narrative as it possesses no direct myths and few cult signifiers to it, to have more to do with highlighting the direct role as illuminators and initiators within the mysteries and their iwn cultuc relationship to food production and relevancy to spiritual salvation. This is not like how Hekate and Dionysos are also addressed at times as members of her core family. This makes it a very specific allegory is the mystic narrative by producing this role of Leto, which further clarifies Leto’s afore mentioned association with myrtle.
Otherwise Leto’s nature seems fairly unchanging.