You can tell if a pair of women's leggings fits well or not by the way the leggings wrinkle. If it wrinkles, it means that your leggings are either too tight or too loose. If they are too tight, you run the risk that your leggings may not be opaque.
Especially with leather leggings, you should make sure that they fit properly. If they are too tight, the leggings can quickly look too squeezed and no longer look elegant.