All I'll say is, yes there are conditions that will cause less than optimal towing experience.
But, it's pretty easy to separate the opinions of those with a lot of experience towing/driving heavy vehicles or combinations and the weekend warriors who sit at a desk 300 days a year and tow a camper once in a while.
It's all about comfort level and setup. Comfort level being key.
One persons description of sway is different than another's.
For example, I consider "sway" to be the uncontrollable swaying that happens sometimes form a bad setup that gets worse and worse until you put tension between the truck and trailer and stretch it back straight.
Others may consider the minor back n forth of a trailer that has a tail that like to wag the dog a little bit, to be unacceptable. I consider this normal as long as it corrects itself.