You don’t need “hit” in PvP but it doesn’t hurt either. I would not stack it in the same way you stack “hit” for PvE if your primary concern is PvP.
You are not correct in assuming there’s no resistance to smite. There’s resisting a spell and then there’s damage resistance. I think you might be conflating the two.
A simple google search will get you the answers you seek. There’s too much info out there to start dropping it verbatim in a forum post when you can just do a search.
Good luck!