the problem with ramps is usually going down, not going up. Too steep of a ramp and they'll jump down instead (could be dangerous if the don't have plenty of room in front of the ramp). I've found around 30 degrees to be a good angle for ramps.
the jumping/flying ability of runners varies greatly from duck to duck. Ollie can easily fly up to a 3 foot ledge without a running start. Moxy on the other hand struggles to get 1 foot off the ground with a running start!
Our ducks know to stay in their pen (they are indoor ducks) and only come out when we open the door. It's only a 2 foot wall which all of our ducks except Moxy can easily fly over but they've never left their pen without permission (except once Norie when just fledged. She jumped out of her temporary house and flew into the other ducks' pen)