Mike, when comparing the 19mm Pano and the 22mm LVW, I had the same impression regarding coma as you, but I'm not convinced that this is correct. Eyepieces don't fix coma, do they?
Re field curvature: The parabolic mirror itself has FC and only an eyepiece with matching FC will present a perfectly flat field to the observer. Such an eyepiece would show FC in other types of scopes though. OTOH, a "perfect" eyepiece with a perfectly flat focal plane would show the FC of the mirror in a Newtonian.