I'm basing my replies and overall agreement off of the series as a whole and the statements taken as a single body of indicators:

I would say that Nynaeve is simultaneously one of the most powerful and dextruos possible female channelers, but is so undeveloped in overall skill that she only uses a bare fraction of her potential. In TGS, Min notices that Aes Sedai are so good at humiliating people because they rarely do it out of emotional reasons but just statements of fact, so when Cadsuane says that Nynaeve has proven she can be of some use, it burns Nynaeve so much because Cadsuane was right - Nynaeve, for most of the series, had been willfully ignoring anything Power-related except for Healing...she had been keeping herself ignorant and near useless. She's recently started taking herself to her limits of her own volition, without the antagonism of a Moghedien to spur her own, and thus we get moments like that in WH, KoD and her detective work in TGS. It is fitting that she seems to come back to her traits as a Wisdom with new strengths while working on her own weaknesses.

I think that Aviendha, Egwene and Elayne together are powerful enough to match Rand at full strength. I think they form a rough 'holy trinity'/3 phases of Goddess-hood: Aviendha - the independent Huntress, Elayne - the mother, Egwene - the priestess or wisewoman.

To that degree, any two of those three women Linked could probably overwhelm Nynaeve. I think the only reason Aviendha and Egwene failed against Lanfear, for example, was because Aviendha was not at her full potential, and it wasn't clear if both had Linked before, in my interpretation of the events which were told from Rand's POV, Lanfear Shielded and held them with Air.

The main conclusion I draw, though, has more to do with a tension between what the author wanted strength in the Power to reflect and how it has appeared in the series. It seems to me that there is a certain strength level where you are strong enough to be a threat, no matter who you face, and I believe Egwene, Elayne and Aviendha are exactly at this boundary.