Most mouth brooders are African cichlids, though there are a few others like P. typus, a Tanganykian catfish. After the eggs are laid and fertilized the female picks them up and carries them in her mouth until they hatch and develop into free-swimming fry. typically the female doesn't eat the whole time. In the case of P. typus both parents take turns holding the eggs/fry, so the female doesn't starve through the incubation period.
Rainbows, tetras, and barbs are egg scatterers, they simply drop their eggs, and in most cases the eggs are quickly eaten by other fish in the aquarium.
Most other cichlids are substrate spawners, some prefer a cave, others a rock to lay their eggs. Usually both parents share guard the eggs and then the fry up to some stage of development, may eat the eggs/fry then spawn again repeatedly until they sort out their roles. Pleco's are similar, though in their case it's only the male that guards the eggs/fry until they're free-swimming, but they're much less likely to eat their own eggs. Sometimes the male does kick the eggs out of the cave, but they usually improve with practice.
Generally speaking mouthbrooders are about the same as livebearers as far as difficulty with spawning/raising fry. Substrate spawners are generally easier than scatterers, but the size of the eggs and resulting fry varies. Some are large enough to feed bbs when they hatch, some are quite tiny and need a week or two of nearly microscopic food before they're large enough for bbs.
Live plants like hornwort or Najas are helpful for tiny fry because they support quite a supply of the micro critters tiny fry can eat.
