About Hugh
We don't learn much about the character in the movie. We do know that he is an old friend of Sean Ambrose.
Sean tells Hugh that "some have the burden of sex to deal with". Which suggests that Hugh hasn't a very active sex life.
It seems also that Hugh, can't really comprehend Sean's desire for Nyah. He distrusts her openly and can't understand that Sean isn't more careful around her.
He is loyal towards his friend and shows a very dedicated and professional handling of his job. Too bad that the villains always have to act below their capacity to ensure that the heroes win at the end.
Hugh would have bagged Ethan easily! Not to mention that Hugh is way taller than Ethan Hunt and thus the mask exchange wouldn't have worked, because he would not have fit in Ethan's clothing and his would have been too large for him.
We also know that the leather jacket looked much hotter on him than on Hunt.