Egg laying ability is inherited. If the parents come from flocks that are good egg layers the offspring will probably be good egg layers. If they don’t lay very well you might be disappointed.
I find strain to be much more important than breed. If the person that picks the chickens that get to reproduce select with certain criteria those traits are going to be enhanced. For example, some strains of White Orps are going to be much more likely to win a prize at a chicken show than others. Some strains are going to be much better egg layers than others. It all depends on what criteria the breeder is using.
There are two basic ways to make a solid white chicken genetically. There is no way to know across the internet which way was used to make your White Orp. If it was dominant white you should get all white chicks from that cross. If it was recessive white there are different possibilities. The odds are pretty high you would get all black chicks from that cross, but recessive white could be hiding many different things genetically. You could wind up with barred chicks or some other surprises.