I think most of your questions have been covered. Pekin is just one breed of duck and only comes in white. If you have two males of any breed of duck, especially if you do not have a large flock, I would expect fighting at least during breeding season. If you have a male and a female of any breed of duck your female's eggs will likely be fertilized; the only way they will grow into ducklings and hatch is if the are incubated (kept in the perfect conditions, temp, humidity for approximately a month) which is either the mama sitting on them consistently (which she may or may not do, depends the duck) or you put them in an incubator. If eggs are fertilized and you do not want ducklings, you just collect them from the nest daily and you can cook and eat them like any other egg. Each Tractor Supply and/or other ranch store that supplies ducklings may have different orders placed to different hatcheries. Some have ducks separated by breed, some have ducks separated by sex, many have all the ducklings just mixed together. Your best bet is to ask at your local store and see what they normally do. By me at TSC they are usually mixed breeds and sexes, but at my Murdoch's they supply sexed female Khaki Campbells generally and no other breeds. If they say they order "pullets" it means all females (occasional mistakes happen) if they say they order "straight run" it means a mix of males and females and there is no way to know which you are really getting.
A good website for breed info is Metzer. You are also able to order sexed ducklings of many different breeds from them. They do orders as small as two, so you could pick the breed you want and just order 2 females if you'd like. You will pay more for this, but will get exactly what you decide you are looking for.
http://www.metzerfarms.com/
There is good duck info on BYC in 2 places:
https://www.backyardchickens.com/articles/category/ducks.30/
https://www.backyardchickens.com/threads/ducks-sticky-topics-index.256233/
Good luck!
A good website for breed info is Metzer. You are also able to order sexed ducklings of many different breeds from them. They do orders as small as two, so you could pick the breed you want and just order 2 females if you'd like. You will pay more for this, but will get exactly what you decide you are looking for.
http://www.metzerfarms.com/
There is good duck info on BYC in 2 places:
https://www.backyardchickens.com/articles/category/ducks.30/
https://www.backyardchickens.com/threads/ducks-sticky-topics-index.256233/
Good luck!