The first is the rack tube/pannier hook interface - the correct spacers should be reasonably snug - but it depends on the rack tubing size. Jandd uses 3/8" tubing for that rack I believe which is 9.5mm in diameter and Ortlieb spacers are for 8, 11 and 16mm so using the 11 mm inserts will leave things a bit loose. This isn't a big deal, but I have used a special electrical rubber tape from Home Depot that just sticks to itself and put a couple of wraps of that to take up some space... it doesn't need to be that tight or it'll be too hard to get the panniers off. Regular electrical tape can work - but I don't like to put tape on things as it leaves a gooey residue.
Next, the placement of the hooks should be such that the bags can't slide along the rails. So the hooks on the panniers should be at the ends of the rails so they can't slide. Ortlieb panniers have an easy and wide range of adjustability of those hooks.
The final adjustment of the lower clip should be arranged so that you can slide it behind one of the bars easily and remove it easily. It seems to work so that I'll put one hook on the rail and tilt the pannier and then slide it down so the lower hook fits behind a rail as the other clip drops on the top rail.
I hope that makes sense...