I know there's an english mastiff, a bull mastiff, and a neapolitan mastiff. Are there any more? Also, what are the different personality traits in the different breeds?
Many types! Commonly called collectively a "Molosser breed"
Olde English mastiff
Italian Mastiff (cane corse)
South African Boerboel (African mastiff)
Dogue De Bordeaux (French Mastiff)
Dogo Argentino (Argentine Mastiff)
Fila Brasiliero (Brazilian Mastiff)
All these breeds are Molosser type dogs and are specifically bred for guarding. they are great guard dogs not only because of their size and presence, but also because they are not BITE HAPPY, but rather possess the ability to knock down and hold.
Each breed was bred for a slightly different purpose… so research each to find out which is best for you.
For example, there is a HUGE difference between the Boerboel's (African Mastiff) temperment, disposition and activity level and the English Mastiff's…. each must be studied if you are looking for a specific pure breed of mastiff.
A heavy hand is NEVER the way to train a mastiff, it has been said that mastiffs respond well to proper training and are easily trained, but will be inclined to react with aggression if aggression is used to train them.
Bullmastiff FYI is not a mastiff breed, but rather it's own breed of 40% English Bulldog, 60% English Mastiff.