FIRA is not well situated and it takes quite a while in metro. And the food options are so poor too.
I had a conference back in April and stayed at the Sofitel. It was about 7 minutes walk - 30 minutes metro with a transfer - 10 minutes walk to FIRA. Still, I prefer to stay in the city and not in that area. But it’s probably easier if you stay around Catalunya.

Airport is doable by metro but I took a taxi. The highway access is quite easy from the hotel.