Welcome!!
I’ll be honest, I have no idea where I would put them in that.
While I do read a/b/o stuff, I’m very critical of it when I do, and will turn back if it’s going a way I don’t like, which is, tbh, very easy for a/b/o stuff. I mostly look for stuff that gets into the world of it, and is less about the actual sex stuff. So, it isn’t really a universe setting I think about much.
For where Lucy/Maggie/Alex could go, I think arguments could go any way. I’m sure most people would go Alex Omega, Maggie Beta, Lucy Alpha because that matches the top/vers/bottom pattern a lot of people write them in.
But, as I said, arguments could be made for any combo, esp with how the plot goes, if it is a new thing to humans, if any suppressants are involved, stuff like that.
I see your tags of Alex as a beta being new and interesting and give you this AU in which Alex and Maggie don’t meet as they do in canon:
Alex has to hide her disappointment when she learns she’s a beta. No one cares about betas. Alphas are the large and in charge ones, and omegas are the only ones alphas ever look at. Neither wants a beta when there’s a chance to get the other. She knows she’s just gonna have to settle for another beta. And, sure, there might be a beta she actually falls in love with, but she is bitter about being ignored by 2/3’s of the population.
(Sometimes, Alex can convince herself she would’ve made a shit alpha and too desperate an omega.)