who are the characters in the story
In Tolstoy's story about the Three Hermits there are many unanswered questions. One of the signs of great literature is that it does not answer all of the questions for the reader, it leaves that to the reader. Tolstoy is a master at this and this is one of his examples.
As to the identity of the three hermits, the debate as to their identity is one that continues. I will share with you my interpretation.
In the fisherman's story there is no indication that the three are anything but helpful humans. Their physical description and their actions do not reveal any hint as to anything more.
The archbishop's meeting also does nothing to indicate that these are anything more than good men.
But the events at the end of the story (which I will ask you to re-read closely for yourself) include elements and behaviors (glowing light, walking on water) that are typically reserved for only divine entities.
Some would say that this leans toward an identification of these three as perhaps the Trinity, while others say that the whole point is that mere humanity has the potential to approach the divine when it encompasses true goodness and spirituality.