I can't compare shock brands...no experience with Konis. I put Bilsteins on my RAM 1500 at about 60K miles, and they completely transformed the truck from a typical wallowing, porpoising RAM pickup to a taught, secure, corner monster. No, they didn't turn it into a sports car, but they did remove all of the factory-shock wallow. Every wheel motion is snubbed nicely, but they aren't harsh. 32,000 miles later, I still love them.
No experience on adding a "sway bar," but cornering flatter is always a nice thing, especially with a top-heavy RV. An important consideration is that adding a sway bar to the rear axle alone will make it "looser" (more inclined to oversteer or slide). Adding one to the front axle alone will make it push or understeer
. When modifying the suspension with anti-roll bars, it's best to get professional help to ensure you maintain or improve the vehicle's handling balance. You might need them front and rear, but if your rig tends to push (understeer), the right anti-roll bar can make the handling more responsive and the cornering a bit more flat.
A case for air bags as an alternative to Sumo springs.
I will praise the Firestone Airbags (similar in purpose to the Sumos). These, too, completely changed the truck as a TV. No matter how I load the truck, I'm able to level it up, and the spring rate is just right for the load. If you have variable loads in your RV, I suspect you'll be VERY pleased to have "more spring" when you need it and no "extra spring" when you don't.
The Sumos are passive (no user involvement), and the bags require adjustment, but you can get bags with a small built-in compressor to take some of the work out of the adjustments. Just push a button to add or release air.
Passive extra springs have been around forever. Many trucks have "overload" springs that engage once the load in the truck sags the rear end enough to engage them. I believe that Sumos work in much the same way...they don't "engage" until the rear sags enough to bring them into play. Air bags are different. They are there all the time, from the first inch of suspension travel to the last. You don't wait for the suspension to sag enough for them to engage.
The secret to air bags is to measure the height from the road to a fixed point on the vehicle...say the bottom of the hitch receiver or a known spot on a rear wheel well...and add just enough air to return the vehicle to that height when loaded for a given trip. The bags add "just enough spring" to return the ride height to its unladen position, and this, in turn, restores handling to very close to unladen performance with steering geometry and so on right where it should be...and your headlights don't blind oncoming drivers. They take out ALL the rear wallow and porpoising as spring rates change with travel.
You're situation is a motorhome, but for a TV and trailer combo, a WDH (weight distributing hitch) can achieve a lot of the same effect and further stabilize the trailer. But bags also come in handy when you're not towing but hauling instead.
Sumos are a great option. Before you take the leap, you might want to look at air bags and compare. There's no wrong choice.