So that's a bit of a fundamental question. Given that we know that channeling is genetic, there must be something physical that affects your ability to channel, it seems therefore unlikely that a bodiless individual would be able to channel more and better than their real body.

I do think that dreamwalking channelers only believe that they are channeling, which may explain both why their ability to channel vanishes when caught in Nightmares, and also why Moghedien was absolutely terrified of Rand and Rahvin being present 'in the flesh' - they were throwing the One Power about, whereas Moghedien and Nynaeve were only pretending to throw the One Power about.

Of course, that's just my hypothesis, and I really have no absolute evidence for it, but I do think it is more likely.