[JRTJH]

Significantly better ??? That depends on the rig, how close you are to maximum capacities in GVW, GCWR, GAW, and hitch weight. It also depends on the type hitch you have, often a 2 point WD hitch is just no match for a combination and you'll get sway with any tow vehicle. On the other hand, a 4 point WD hitch may not control sway in a rig that's not set up properly or that is simply "outclassed" in any of the above "maximums"....

That said, from a control standpoint, the longer the distance from the rear axle to the front axle, the less impact and "equal distance" from the rear axle to the hitch ball will have on sway. Lateral forces on the hitch ball will "push" the front axle of the tow vehicle in the opposite direction from the forces on the trailer ball. The further the front axle is from the fulcrum (rear axle pivot point) the less impact you'll feel in the steering wheel.

So, generally speaking, all other things being equal, yes, the longer the wheelbase the more stable the rig will be.

A fifth wheel does not "induce front axle sway" because there is no fulcrum. The trailer connection point is directly over the rear axle (or very near directly over it) so there is no push/pull in the opposite direction.