The Quincy in general, have developed their abilities to eradicate hollows of any kind or level. So, whether it be Vastolordes, Adjuchas or Gillians or regulars, they are on a different level period.
It was confirmed that the top 4 espada were all "Vastlorde / Arrancar". And that's from Stark to Ulquiorra. Who was the strongest of the 4 is a another debate for a different forum, but a VL being capable of using Quincy powers would be something else entirely.
Espada 1-4 were VL, although only Harribel was the only confirmed one...
I think the top 4 Espada were Vasto Lordes but maybe not at their peak, Ulquiorra gained a second transformation maybe the others would have too & whose to say there's not a third transformation.
I also think maybe Aizen unnaturally upgraded them to Vasto Lorde level with the Hogyoku so they weren't at their top strength, not enough time to mature the power similiar to Ichigo & his new Bankai sword.
Actually, the whole Espada timeline is prety muddled. Grimmjow was Numero 12 I belive, which would make his pack the first Arrancar in Aizen's army, but Baraggan was apparently the first one he recruited, yet Aaroniero is described as "the last of the 1st generation Espada". Doesn't make much sense, really. But it's clear that the Espada were lurking in Las Noches for a fairly long time. Nnoitra is a clear example of the Espada growing more powerful with time and experience. His zanpakuto even changed since his flashback, much like Ichigo's.
I remember reading it somewhere... I think it was in the last databook? Regardless, Shawlong was Numero 11, I think Ylfordt was 15, and the rest were in the same region number-wise. Grimmjow's whole pack had the lowest numbers excluding the Espada, meaning they were the first of the Numeros, and unless Grimmjow abandoned them sometime before meeting Aizen, he must have been with them when they came to Las Noches.
My understanding is that the top 4 Espadas were Vastolordes. And Aizen's goal was to use the hyougyoku to increase their strength, and make 6 others into Vastolorde-level hollows, too. That way he could have the 10 VL that Hitsugaya said could take out all the captains.
But in the end, they were all much weaker than Aizen hoped. That's basically what Aizen said when he cut down Hallibel.
So, I think the most we can hope for is one or two of the former Espadas to have gotten stronger, and maybe help fight the Quincy.
The databook was ambiguous on the matter. What it said could have easily meant that the espada were comparable in power to VLs which would imply that as hollows they did not quite the power of a VL. Ulquiorra was revealed to be either close or an actual VL however the manga pointed out that he kept his HSR in exchange of the power he would have received otherwise on top of adding a second stage of release on him. As far as barragan and starrk, they were shown as arrancar before joining aizen so we will never know if they were at any point in their lives actual VLs.
I wonder if aizen had hoped the top espada would be able to handle the actual royal guard.... I guess that if they were unable to handle the captains then they were indeed useless to him as they would not be strong enough to fulfill the role of royals once he took the seat of the king. 0, 1 and 2 seemed to be well above the usual captain level (yami was defeated by kenpachi and byakuya and still managed to hurt them, starrk fought a total of 4 different captain level enemies and barragan had an insanely hax ability and made relatively short work of soifon). If the royals are as strong as they are said to be then naturally aizen didn't have need for them if they were unable to defeat the captains.