[Whewt22]

Yea, I see no evidence leaning Ulq or yammy in the Vastro Lorde direction. Anyway I think its too obvious yammy wasn't a Vl considering Ichigo took him on without effort, and lobbed off his arm. Considering what we already know, Vastros alone are stronger than an average captain, but yammy was an arrancar, there just no way he was a VL previously.
Tops I see maybe the first 3 espada being VL, only evidence I have supporting this would be the ex espada. The former espada could have been kicked out by the creation of Vastro lorde arrancar.

So basically thus far we have;
1.Vasto Lorde is the most powerful form of hollow. A hollow can be a Vasto Lorde without being an Arancaar. Aizen turns them into Arancaar, but they were already a Vasto Lorde before ever meeting Aizen. They can also take it apon themselves to remove their masks, but Aizens method s more efficent and guarnteed.

2.Arancaar are beings with Hollow and Shinigami powers. They already had hollow powers and Aizen gave them Shinigami powers as well. Unlike the Viazard who started with Shinigami powers and then gained Hollow powers later.

3.Espada are the 10 most powerful Arancaar. So all Espada are Arancaar, but not all Vasto Lordes are Arancaar. There are some Vasto Lordes who are still only hollows.
AND
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1) Vasto Lorde are not Arrancar. Vasto Lorde are the elite of the Menos class. They have a humanoid type body, but they still wear their masks. The other two class of Menos are Adjuchas and Gillian (Gillian being the weakest).
2) When a Vasto Lorde gains Shinigami powers (by way of removing their mask), they turn into Arrancar.
3) Not every Arrancar looks human. Some still have the appearance of their original Hollow body. Such as Grand Fisher, who was an Arrancar, but looked nothing like human (when Isshin fought him, not when Ichigo fought him).
4) Any Hollow can become an Arrancar if they remove their mask and gain Shinigami powers. However, a Menos will obviously be a stronger Arrancar than a regular Hollow turned Arrancar (I question this part, but Grand Fisher was not a Menos, at least not to my knowledge, and he became an Arrancar).
5) When a Vasto Lorde becomes an Arrancar, they are guaranteed to take the form of a human. Adjuchas and Gillian are only a possibility to take the form of a human.