Don't forget about dexterity vs strength. I'd posit that she is merely remarkable in strength, 70-80 in that 1-100 scale, but she is a 100 in dexterity.

I think Cadsuane's comment is more along the lines of Sumeko can do some of the stuff Nynaeve can do, because shes a 100 in this one very small specific thing, honed over time with very small amount of power.

Who knows, and I doubt it, if she could perform ALL of the healing that Nynaeve can do. If you're so strong and very gifted, why would you learn to sip the power, as Cad alludes to when Nynaeve uses the well in Far Madding.

The other side of the coin and one that I don;t think has truly been considered before now, is how much of all of this is a mental block self imposed on yourself.

We see time and again some random channeler who does something the tower never thought possible, and I think its because no one was there limiting them from the beginning as Aes Sedai do with novices. Nynaeve truly believes she can heal anything, and so she finds a way. Perrin knows he is the master of Tel'an'rhiod, check my spelling, and therefore he is and has had practice being the master. Couple those things together and you have someone who might not always be the most elegant with her flows, but she has no mental block about what she cant do.