Au'ra aren't related to voidsent or dragons. The artists took visual cues from dragons and demons. Miqo'te take visual cues from cats. They are not in any fashion related to cats. No one's going around "hey did someone cross breed a hyur and cat to get Miqo'te. No they are a 'natural" part of the world.

Au'ra are like the other pc races likely Placental mammals, thus have the features of such and don't lay eggs.

On the otherhand I will totally argue Dragons in this game are Monotremes and not reptiles.