Fact is. A properly balanced TT with a properly adjusted WDH will NOT sway. Sway being defined as the trailer beginning to move back and forth on it's own while running straight down the road. That should NEVER happen at any speed. If is does you have other problems.
It should not sway even IF you have NO sway control. IF it does. Again, you have other problems. Find out what the problem is and fix it. Be it low tires, poor balance, or incorrect hitch. AFTER you fix the sway problem. Get it to run with no sway at any speed. Then and ONLY then add sway control.
Sway control is for those time when sway is induced by dodging a child, deer, or other vehicle. I use sway control just for those time. I have O sway with my TT.
So to answer your question. You should have O sway. Will you feel the TT from time to time? Like in a strong wind, or when another vehicle passes Of course, but it should never pull you around. Never cause you alarm.