Real Sociedad might be a team that lack of strength, but that's fine since they have a good defensive too. At least they have a chance to beat PSG even though it looks competitive, unlike most of people who think PSG will obviously win the match.
Based on history, PSG's performance was really poor during knockout stage, they only very strong during group stage.
Real Sociedad does not have any chance of winning PSG even though their defense is strong, PSG is capable of passing through their defense with the help of Kylian Mbappe, Dembele and Kolo Muani
Why I say so is because Real Sociedad they don't have any good attacker that can hold their forward very well, secondly they don't have good midfielders compared to PSG.
Based on history PSG performance was not that poor at knockout stage and i believe they are strong in both stage.