Having ducks, I think its super important to plan out the housing, you are wise to think ahead of that now. I personally have an indoor/outdoor setup for my ducks. The inside we use in bad weather and also as broeder area. Some of the flock seem to just prefer to fo in there sometimes too. The outside pen's dimensions are 12'x24',x7' (2x4&2x12 frame), triple layers chickenwire and hardware cloth, buried 18" underground, inside this structure I have a repurposed kids' playhouse. Everything outside is all non-permanent.'.. in fact, I am considering moving things this year to a different spot in my yard. (More on that in just as second!) The big thing with your pen IMO is that you(or whoever gets cleanup duty) will need access. So while your ducks might be perfectly happy if the pen was only 4' tall., you wont be. A chickenwire fence IMO is a very temporary thing. It will not offer any protection from predators, and in all likelyhood, as soon as ducks reach maturity, they will be over it any way. So the reason why Im considering moving things around this year is pretty simple: Ducks are messy, they destroy any trace of vegetation. So in this regard, having the flexability to choose where they will range any given day is a great thing. Or plan on a substrate like pea gravel over landscape cloth. Do not skip the landscape cloth, I did that last year and noiw my pea gravel is nowhere to be seen. I have personally heard wonderful things about using electric at the very top of enclosures for predator protection, never thought of using electric for containment and would not. Your ducklings will be wet and messy, I will advise you to just go with Rubbermaid now, that is what I've done. You will want absorbent bedding, I've used pine chips, shredded newspaper, pine needles, but my favorite is is straw. Do search in the learning section and you will find what works for you.
Oh yes, those breeds should be just fine together. In my profile pic, the tall guy (b&w), he is a Pekin x Khaki, That is my Khaki drake in front of him, and one of the Old Ladies (Pekin) to the left. The only thing I have found is that the Runner might not be as strong of a swimmer as the rest, altho my opinion is that if all are basically hatchmates together at the same time, they should all be fine. Enjoy.