For a lower cost option the Axiom panniers will work plenty well for your needs. They are water resistant(they do have a water proof model for more money). If you need water-proof, get some white trash compacter bags and put your stuff in them inside the panniers. They have a Rixen & Kaul rack-lock on each bag that works well. The bags won't bounce off your rack.
With respect to the Ibera rack..this one
https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1
is nice as it has the racks to hang panniers are a bit lower than the upper rack surface. This makes the bags easier to hang with gear on the top rack and it's easier to secure something on the top rack without the panniers getting in the way. My girlfriend has used this rack on several tours and it works perfectly. Stout tubing and good welds. I have a Blackburn that is nearly the same as the Ibera. Same size tubing, same weld appearance, cost 3x more.
The Ibera rack/Axiom panniers combo is all you'll ever need. If you had more extensive use in mind..then the Ortlieb route is probably a good investment.