There is no difference if Barcelona is in the runner up or third position because it is the same as getting a UCL ticket next season. The point is to be in the top four, you don't have to be in the runner up position and to maintain it, the point is that being in the top four is more than enough. Moreover, even though Girona managed to overtake Barcelona without any results, it's still the Laliga title for Madrid and UCL tickets for the four teams in the final standings, Barcelona might also focus more on the UCL because they have a chance there.
Barcelona knows enough that they can't catch up with Madrid who are at the top of the standings, that's why they are more focused on the UCL for now and I'm also sure that Girona wants to maintain their position in the top four and it will be impossible for them to overtake Barcelona, who are still playing very well so far. consistent until now, so there will be no chance for Girona to overtake Barcelona, against PSG it will certainly be a difficult match for me. Barcelona is more focused on thinking about how to get through to the next round and beat PSG.
The point is, Barcelona must maintain its ranking in the top four of the La Liga standings. Since Barca is currently in the runner up position, it is appropriate for them to maintain it rather than experience a decline in ranking. Moreover, if Barca loses momentum towards a Champions League ticket. So, it's natural for Barcelona to defend its title, especially since Barcelona is one of the elite teams in this competition. As for Girona, they could overtake Barcelona's position. However, with the same unstable performance, plus having several crucial matches, it seems difficult for Girona to become runners up until the end of this competition. After all, as you said, the most important thing is that staying in the top four is enough to be able to compete again in the Champions League next season.
By the way, that doesn't mean Barcelona can't catch Real Madrid at the top of the standings with 8 games remaining. However, it will be very difficult for Barcelona, considering the condition of Barcelona itself, as well as Real Madrid's performance which is currently in a positive trend. So, the most ideal thing is to maintain consistency in La Liga and do his job with his best game in the Champions League. because, to overthrow Paris Saint-Germain is not an easy matter. There are not many choices, Xavi must focus more on the most ideal position for his squad. At the very least, in Xavi's final season with Barcelona, he must do his best, including overthrowing PSG in the quarter-finals.