Porto will try defensive tactics because they already have the advantage in the first leg. Porto can play very well with their defense. This can be seen from the first leg. But Arsenal played as host in this match. That will give them additional morale and motivation to win the match. Even though it was difficult to win the match against Brentford, I think the match against Porto will be different because Arteta will really prepare a strategy and Arsenal will go all out to win the match. I predict Arsenal will progress to the next round.
Having a narrow lead of one goal in the first leg is still not necessarily safe for FC Porto in the second leg which they will play tomorrow. Because Arsenal is also a quite dangerous team when playing in the Champions League with the motivation of being the host, FC Porto still has to try to score a goal in the second leg even though they also have to make a fairly good defensive strategy because if the lead is still very small, of course FC Porto themselves must be aware that they still need to fight hard at home to Arsenal.
It does not guarantee that they will be safe but if in the end Arsenal do the same pattern as in the first leg then Porto's situation is much more favorable.
Arsenal's scheme was actually quite good where they had possession of the ball and several times initiated attacks in the first leg before but their finishing was poor which made the opportunities created none on target they got and if their performance in the second leg will be the same as what they showed in the first leg then I certainly doubt Arsenal can make a difference at the Emirates later.
But Arteta also seems to be aware of that and in recent weeks in the domestic competition they have changed enough where the quality of their attacks is better and this could be a good weapon for Arsenal to provide different results and reverse the aggregate in the second leg.