I tend to think most Author quotes regarding Strength speak to potential. Seems a little strange for RJ to have created a rolling list based on Nynaeve's current strength ... He'd have to constantly update it and while it's clear he had a pretty good sense of where his major characters current strength was in any given scene, he tended to build situations to demonstrate a strength increase. For instance Elayne spending weeks on a Seafolk ship weaving huge flows increased her strength. She openly notes it and is surprised when she is now strong enough to lift a woman. Another clear indicator that Elayne was significantly weaker than Egwene at this stage ... In the same time frame Egwene is already stronger than Moiraine. Elayne was probably no stronger than a middling Sister in TSR. A few months later in the Rebel camp we see another significant jump in Elayne, who is now clearly Stronger than any Sister in the camp.

Character POVs are obviously up for debate ... Alivia may have been "considerably" stronger than Nynaeve in the moment (and from a much weaker persons POV), but at full strength the differential may be significantly smaller. I tend to think we get a mix of current and potential comments from characters, but generally they point out when they are speaking of potential... As Egwene noted when she commented that Sharina was stronger than Nynaeve or Elayne when she talks about matching Egwene. It's possible Tamela and Viendre are not as strong as Elayne in potential, but were only stronger at that moment. I tend to think they may not have more potential, because Elayne didn't call it out, but it could as easily go the other way, but women that close to Someryn would discount the comment on her never having met someone even close to her in strength.