For us, the answer is - they help some
. In fact, I'm still not happy with the lack of shake in our rig.
Right now- we use a between the wheel chock (RotoChocks). And, a JT StrongArm knock-off called UltraFab Eliminators.
I've started trying a product called the Valterra Stabilizer Stand. It doesn't seem to be helping. My wife thinks it is worse with it, but I think she's wrong on that account. But, it's definitely not helping.
My next step is to add scissor jacks under the camper near the axles. They'll be a hassle to setup (the Stabilizer Stand is, that's for sure) but if it helps with the stability, then it'll be worth it for longer stays (more than a weekend, I mean).
More detailed write up here:
Learn To RV: Shake, shake, shake - RV Stabilization