Actually they are quite similar in the way the spawn. Of course you wouldn't want to house these two together. Usually with kribs you can get a male and a female, but sometimes planned marriages don't work, and it is easier to buy juveniles and let them pair off naturally. Same with the firemouths, buy 6 juveniles and let them find their own mates.
They are both substrate spawners, and the kribs prefer a cave with a smaller opening, while the firemouths make take a 8" flower pot on its side. They will both take care of their eggs and young, it is fascinating to watch.