The three devices serve difference purposes (I'm assuming you are talking about a motorized RV, which is really a light to medium duty truck with a huge box.
What you call a sway bar is an anti-roll bar, a torsion bar that uses the tendency to lean towards the outside to lift the axle on the opposite side, in the hope that there is still enough load on that side to roll back that direction. With really strong anti-roll bars, and tight enough corner, the result is to lift inside wheels off the ground, something you see in road racing of small sedans and crude sports cars of 1950s to 1970s when everything still had truck suspension.
E350 has a front sway bar, E450 has front and rear. Aftermarket you can add rear bar to E350, or get stiffer bars. In racing cars with crude suspensions, we adjust anti-roll and one end or the othrr to adjust understeer vs oversteer. The stiffer the bar, the less ultimate grip (because we are pulling that inside tire up off the ground) so if we want to loosen the rear we stiffen the rear sway bar.
RVs don't usually operate near cornering limits, so the question becomes: do you have a problem with too much body roll? Factory antiroll bars were sized for stable handling at 80-90% GVWR, but you could have a problem with front to rear weight balance, or higherCG in the rear.
Track bars. On a motorhome chassis we are usually talking about a Panhard Rod, which helps to more firmly locate an axle laterally, which is otherwise located only by the leaf springs (Hotchkiss suspension, almost universal in light trucks > 1/2 ton for the last 70 years). Side to side looseness (fractions of an inch) are responsible for what we like to call sway, side to side movement of ther rear end. The Panhard rod doesn't stop movement, as its geometry forces a movement of its own, but what movement there is is more predictible, more controlled, than movement on the leaf spring mounts.
Really light trucks, compact and 1/2 ton pickups, use the shock absorber (damper is a better word) mounting geometry to help manage sway, and axle windup (another problem with Hotchkiss design, for which there is another product sold for correction, also called a track bar).
If you feel the rear end shifting in curves, Panhard rod/track bar might be the solution.
Third product you mention is a stabilizer, marketing name for a passive steering damper. A damper mounted between frame and tie rod, it filters out or resists small, quick steering movements, while offering less resistance to the slowet, larger movements used in turning.
Another device is sold as a stabilzer, and that is a set of springs to resist all steering movement off the springs' relaxed point. If properly adjusted, these can help keep the wheels in a going straight position when push away by conditions like sidewind, rad crown, or bumps in the road. The springs may not always provide the right corrections, but most of the time they do part of the work you would have correcting steering for these conditions. They'll also resist your efforts to deliberately turn, but you'll get used to that, and you have power steering to help.
If centering springs are not properly adjusted for the roads you drive, you may be fighting their corrective efforts from time to time.
Some owners also find it usefull to change shock absorbers (dampers) to a different rate and ratio, or to change to tires with differenrt roll stiffness or yaw stiffness. Sometimes it is just a matter of adjusting tire inflation pressures.
Have you observed a particular problem that you need to solve? I have a E350 van and a 12,500 pound motorhome on stock E450, have found no need to modify either, though I got a handling improvement going to stiffer tires on the motorhome.
If you are talking about pulling a trailer, sway bar means something different (a friction devide resisting yaw at the hitch) and stabilizer usually means a different solution using spring pressure and geometry on a weight distributing hitch.
Tom Test
Itasca Spirit 29B
