Breeds I've had mixed in with my chickens without problems:
-Swedish
-Khakis
-Cayuga
-Silver Appleyards
-Gold Star Hybrid
-Crested
-Australian spotted
We mostly keep ducks because we prefer duck eggs to chicken eggs but I always have 6-10 chickens to provide eggs when the ducks aren't laying, to provide eggs for a handful of recipes that can't handle the higher fat content of the duck eggs, and for bug control since they seem to eat different types than the ducks.
I've introduced it every which way without problems...ducks first, added pullets, had old hens, introduced barely-feathered ducklings, introduced adults to adults. I've never had the problems introducing ducks & chickens the way I've had with chickens to chickens. For that matter, I've never had problems ducks to ducks either.
I'd get whichever breed you like the most. I always want Khakis for the egg production & predator evasion abilities but my husband always wants something prettier so we usually have a variety.