George, I assume that they mean average speed, because 16mph is not a particularly fast top speed. I'm no touring tank, so my average speeds are around 12-16mph, including brief stops to soak in the world. But top speeds are significantly higher. For example, on a flat trip to the beach on my Trek 7200 FX with 25lbs. of gear, I cranked up to 27mph for a short while. Again, the average was much lower though -- I was just pushing to see what I could get up to. From what I've seen, the Randonee should be at least as capable as the Trek and probably more comfortable in the long haul.
This said, if you're touring, don't worry about those speeds. Take it all in and enjoy
The size that you say you're getting is probably ok too. I'm 6'2" with a 33" inseam (I'm all torso according to the wife) and I have a 58cm Fuji Touring. Fits great -- once you dial it in to your reach and fiddle with the handlebars and such. No worries.