Hi. As swathdiver said above, swaying is usually due to not enough of the trailer weight on the tongue of the trailer.
Swaying can be really scary. Fifty years ago I was towing a U-Haul from San Antonio to Oakland. I left San Antonio with a tailwind. Partway into the trip I made a turn in a town and came out of town headed in a different direction. The wind was now a quartering headwind and the trailer started swaying as I accelerated out of town. As I slowed and pulled off the road, oncoming cars were also pulling off the road. I had too little weight on the tongue. I could lift the tongue off of the ball without a lot of effort. I was younger then. I moved several boxes from the rear of the trailer to the front of the trailer, verified I could not lift the tongue off of the ball, and all was well.
You need to start out with the chapter on towing in your Denali owner's manual. Hopefully, you have the Max Trailering Package on your Denali. If you do, there will be a Trailer Brake Controller or Integrated Trailer Brake Controller (ITBC) on the dash just below the instrument panel to the left of your steering column and to the right of the headlight control. The trailer brake control should be pictured in your Owner's Manual.
You may also have an owner's manual for your trailer which tells you how to hook your trailer up to a tow vehicle, what the empty weight is, what the tongue weight is, and what cargo can be carried in the trailer. You should have a data plate on your trailer which gives some of the weight information. It should tell you if a full fresh water tank is included in the trailer empty weight or as part of the "cargo". Same with the propane in the propane tanks.
You should be using two weight distribution bars, one on each side of the tongue of your trailer. They are sometimes called "spring" bars. The back end of the bars pull down on the tongue. The "equal and opposite force" at the other end of the spring bars is "up" on the tongue/hitch ball connection. The weight distribution/spring bars should be set up so that they have some tension on them when the trailer is on the ball of the hitch. See your manual.
As described in posts above, the trailer should be weighed when it is loaded as you plan to tow it. Tow it onto the scale, and then remove it from the Denali, and drive the Denali off of the scale, leaving the trailer tires and the tongue jack stand on the scale. This will give you your "Total Trailer Weight". Then reattach the Denali, and pull the trailer forward so that only the trailer tires are on the scale. This gives you the "Weight on the Trailer Tires".
Calculate the "Weight on the Tongue" which equals "Total Trailer Weight" minus "Weight on the Trailer Tires".
The "Weight on the Tongue" should be 10-15% of the "Total Trailer Weight". If it is not, move some things in the trailer or fill the fresh water tank so that the "Weight on the Tongue" equals 10-15% of the "Total Trailer Weight". In still air, with no crosswind, with a proper amount of weight on the tongue, you should not need friction or hydraulic sway control. But with a crosswind and/or trucks going by in the opposite direction, sway control is your friend.
Hope this helps.