If Arsenal lose to PSG in the second leg it will be disastrous as they will record another season without a trophy in a row. The one goal difference isn’t much, Arsenal have a good chance in the second leg to make history but seeing how poor they have been performing lately in the Premier League I fear they might concede more goals against PSG in the second leg.
Don't think about the EPL game before, it was just a different game. I mean, whatever the result in that match, it will not affect the result in the current UCL match. Because Arsenal's position in the EPL is already comfortable. So we should not doubt any team in this second leg. Because Arsenal can do the same away from home and the small difference in total score is a big hope for Arsenal.
But honestly, if Arsenal qualify for the final round, I doubt that Arsenal can beat Barcelona or Inter Milan. Because mentally Inter and Barca are more experienced.