Someone’s personality is the specific set of qualities and interests that make him or her unique and unlike others. If someone has personality, he or she is lively or engaging in some way that appeals to others. A personality can also be a famous person or celebrity.
Personage is a fancy word for person and because it is fancy, the person is seen as fancy or deserving of a higher respect. It can also mean characters in books or paintings.
A persona is the part of a person that is seen by others. Celebrities especially have a public persona or a way in which they act when they are in front of a camera, as opposed to how they act at home or in private settings. It can also be a character played by an actor or written by an author.
There are two accepted plurals for persona. The original Latin plural is personae, with the last letter making the a change from short to long. The adapted English plural is personas, where the a keeps the short sound. The English plural is the more popular by far, very far. But there will always be the purists that insist on the traditional ending and deem all else incorrect. One should always know the audience and write to their preference.
In short, a personality is the interests and characteristics that set a person apart from others, a personage is someone important, and a persona is a personality that is affected or false.