In a nutshell: everything was perfect. The apartment in itself is super charming, high ceiling with a great feeling of space, perfectly clean and with great attention to detail, extremely quite as the bedroom is located to the inner courtyard.
We went to Rachid's apartment in a semi-professional context so also had the home office experience: here as well, everything's perfect, quality of the WIFI is excellent (we were 2 in video calls at the same time, super fluent), the floor plan is practical and divided in way that 2 people can have a proper working space, and notably speak without disturbing one another.
In the free time, one can enjoy the direct location which is just great and authentic: the street is full of tapas restaurants, with a relaxing and typically local atmosphere (not the first time we came to Barcelona and we were very nicely surprised by the discovery of this neighborhood). Not to mention the close proximity to the beaches and Barceloneta.
Many thanks again Rachid, right at the top ;)