For bad roads, the damping needs to be a bit stiffer to handle those big bumps and avoid bottoming the suspension. You can break the aluminum castings on these Paralevers using too soft of a setting with too little spring preload...ask me how I know!
If I had ESA, I'd find a typical nasty piece of street for a test....Then:
-Start at the loosest setting (1 helmet?) I'd try the "Comfort" setting.
-Then, I'd go back and try the Sport setting to tighten up the damping with the same pre-load.
-Then I'd go back to the comfort setting, change to (1 helmet/full bags) and try that.
-Then I'd try "1 helmet/full bags" with the Sport setting.
-Then I'd try Comfort and Sport with the "2 helmets" setting etc.
By now, you've probably found the "sweet spot" for bad roads, but go ahead and try each setting. It will give you an idea about what these settings actually do. Also read the rider's manual that came with your bike. There is surprisingly useful information in it.
When you have the best setting for rough streets, remember it and use it. For touring and other uses, just sweeten to taste.
The most comfortable setting for any road is the one that uses as much of the full travel of the suspension as possible but never bottoms or tops out. Use just enough damping to slow down the wheel movement to avoid bottoming/topping.
