There's a lot of variables to wheels, weight is one, stiffness another, people tend to use higher spoke count wheels for heavier duty uses. A lot of people tend to build a very strong wheel around the Son28 hub from what I've seen, a rim that can support a semi wide or wide tire for commuting or touring and usually a high spoke count, like perhaps 36h... so it sounds like you're already well on the right track to me.

I'm sure an experienced touring cyclist will be along shortly to fill you in on spoke/rim preferences, and good luck to you!