What little is shown of his personality is displayed in the first three Persona games. In most incarnations, Philemon serves as a neutral observer and he watches as things unfold. He has a benevolent view of humanity, frequently pulling the protagonists of Megami Ibunroku Persona to give advice. At the same time, due to his nature as an otherworldly being of the Collective Unconscious, he does not have exactly the same world view and values as humans, as shown by his willingness to wager their existence on their strength of heart

Though I do not have a preference with his voice, I do believe that he would have a soft smooth voice, however, higher voices are welcomed if they are able to keep the smooth tone to him