I recently read a deep dive on the history of D&D's medusas and had some thoughts of my own.
I prefer to call them gorgons after the original Greek myths, and will continue that usage for the rest of the this post. (The iron bull monster can just be renamed to "stone-breath bulls" or something.) I prefer to treat gorgons as a curse, as per the popular myth, as I find that origin more mystical and customizable than them being just yet another self-sustaining fantasy race. However, the 5th edition story for the curse has problems.
According to the 5e MM, the clients are vain brats who get eternal beauty from the patron, before it eventually turns them into gorgons. Do they know this is the price and, if so, why would they ever agree? What does the patron get out of the deal? It feels poorly thought out to me, so I think it needs revising.
Unless you can find a good reason for it, then ditch the whole patronage thing. Unless the patron is deliberately trying to torment people or spread death, then they have no reason to curse people into gorgons. Instead, make gorgonism a cosmic karmic punishment for women who seek eternal beauty to the exclusion of all else, particularly the health and safety of others. Such a vain women was wicked, used her beauty for evil ends, and resorted to dark means to preserve her beauty, like using dark magic to steal the life of others. So the universe curses her, turning her into a gorgoness.
The curse of the gorgoness, beyond being a hideous monster, is that now nobody can appreciate her beauty. Anyone who looks at her turns to stone. If the gorgoness ever looks at her own reflection, then she too turns to stone. As a result, they become very antisocial individuals.
A gorgoness's appearance is variable but reflects how long she has been cursed. Fledgling gorgonesses still appear largely the same aside from her hair turning into snakes and her skin taking on an earthier tone, perhaps to emphasize the irony. As the curse progresses, she grows brass claws and talons, venomous fangs and tusks, features like a hag, her skin turns to scales, and her legs are replaced by a massive serpentine tail. Some even grow wings like in the myths.
What of male gorgons? Well, here things become more complicated, but not really. See, the gorgoness's vanity was not simply the result of her own wickedness, but also contributed to by patriarchal society's obsession with feminine beauty. Women are socialized to value their beauty, and punished for failing to do so, far more than men are. As such, men who suffer the curse are cursed less for cosmetic vanity and more for general narcissism and arrogance. He becomes a gorghias.
A gorghias doesn't gain the same monstrous combat benefits as a gorgoness does. All his hair falls out, his skin becomes earthy and scaly, and he gains a literally venomous gaze. Those who gaze upon his visage are literally poisoned by him, and seeing his own reflection sends him into anaphylactic shock.
Do gorgons organize? Do they reproduce? No. The curse is meant to isolate them, turn them into a blight on society even worse then they were as mortals. They are immortal and do not reproduce. They don't even eat or drink anymore, instead draining lifeforce with their deadly gazes for sustenance.
But these are just some ideas. Perhaps your gorgons are the spawn of a legendary dragon-nymph like Ceto or Echidna, the creation of a mad wizard like Morgoth or Doctor Frankenstein, or a demon lord's malicious curse on some poor fool. Greek myth wasn't consistent on where the gorgons came from, with one story saying they were spawned by Ceto while another claimed Medusa was cursed by Athena. You do you!
