>What size door do runners need for their coop?
Wide! Ducks tend to all come out at once in the morning, so as wide as you reasonably can, to avoid the crush. Nice and tall too, for runners!
>What type of bedding should I use?
We use shavings, which work fine.
>Do they need drinkers/feeders or do normal bowls suffice?
Normal bowls are fine. Ducks tend to scoop food, so a normal bowl is better than a chicken feeder say, which is more designed for pecking.
Drinkers is a bit more tricky. Ducks need access to, at very least, enough water to dip their heads in to keep clean. If you don't have a pond, I'd recommend getting a dog bath, with a ramp up so they can go for a swim. We have one like this, which was bought as seconds quality, and has now served us well for ten years: