Hotel Eiffel Blomet checks off all the boxes. Nice reception/lobby, swimming pool in the city, which was GREAT when we visited during the hot month of July, minutes from a Metro station, and located in a real neighborhood, which meant there were lots of useful shops nearby, versus just touristy cafes and restaurants.
There was a boulangerie, cafes, pharmacy, Monoprix, grocery store, lots of fresh fruit vendors and even a cute nail salon. It was quiet and safe. The hotel itself was cute: art deco inspired decor, friendly staff, and small but clean rooms. It's not within the core tourist areas like Les Halles, or Marais, but we were a 2 minute walk from Vaugirard station (M12) line and we went everywhere thoughout the city easily.