If by "fares well" you mean is judged most kindly by the narrative voice, I'd say that Mrs. Smith fares the best. She is approved of for her manners even in difficult circumstances.
By contrast, characters such as Sir Walter are openly mocked; he is shown to be foolish, and his concern with social status is the source of much of his foolishness.
The verb 'fare' means "to perform in a specified way in a particular situation or period." The question would mean whether there is an improvement in the class and social status of the characters.
There is no change in the class or social status of Admiral Croft. Throughout the novel he is a respectable retired naval officer.
Anne Elliot who is a member of the landed gentry marries Captain Wentworth a rich naval officer. Although at first sight it may seem that her class and social status are lowered because of her marriage to Wentworth in reality there is an improvement, because her father's estate would anyway be inherited by Mr.Elliot-a person whom she had decided againgst marrying. Anne is not at all perturbed that she is marrying someone below her class and social status on the contrary "She (Anne) gloried in being a sailor's wife."
In Mrs. Smith's case, the only improvement is the fact that Wentworth will be able to retrieve for her some of her late husband's assets from the West Indies.
Sir Walter, a baronet from the landed gentry remains one till the end; however his extravagant lifestyle lands him in all sort of financial difficulties and he is aware that Mr. Elliot will inherit his estate after his death. So, although there is no deterioration in social or class status, he fares very badly financially.