I thought this way obvious way back but it is nice to have a direct statement.

We also see it when Egwene heals Gawyn. She supposedly has abysmal skills with Healing, yet she is able to close his wounds? I think if she'd been weaker, she'd have been less effective at the task.

I don't think Nynaeve can match anything Egwene can do with Earth. After all, Naeff was doing a fairly simple thing with Air. In fact, I highly doubt that Nyn is anything but super-strong with Air (she can listen to the wind, which requires great strength in Air and Water). Instead, she is just less skilled at using the OP, and compensates with her strength.

I think once Nyn reaches her max skill level, she should come close to the kind of things Rand can do with the OP. We know she has it in her to be very very skilled.