This year I bought my first runner ducks, and I am so happy!
I have five black and six chocolate. I cannot answer your question about their feces because I don't get grossed out by manure in general. Hog waste, well, that can be pretty rich. But I digress.
They do make quite a bit of manure for little birds (they max out at a little over 4 pounds, I have read). I am a gardener, so this material is gold to my plants. They love it, I love it. It has a bit of an odor but not really intense. I clean out the brooder at least three times a day, sometimes five. This is just until they are out in their pen and shelter outdoors (waiting for night temperatures to stay above 45 or 50). At that point, because they will be in the yard most of the day, cleanup will be much less frequent, and easier because I will be using shavings and/or straw or similar material for bedding, not towels as I do now.
Runners need a few of each other to be happy - I was told they have a very strong flock instinct, and what I have seen bears that out.
Have I mentioned they are so cute, so fun, so funny, fascinating, excellent foragers (they eat slugs & bugs), lay somewhere around 200 eggs a year?
Mine have not tried to escape their 200 square foot pen. I give them water in a concrete mixing pan (about 4 by 3), some leaves to rustle around in, toss dandelions and chickweed into their water, and they seem delighted. They flap their wings and can get up on their tiptoes while flapping, but so far I haven't seen anyone leave the ground. They run quickly, and usually all together. They might be able to get a foot or two up in the air with a running start, but I think it would appear more like a long jump than flight.