This will be a big match in the round of 16 because after all in terms of experience they can still be said to be balanced, in terms of the quality of their players is also not much different so this is still a fifty-fifty.
As for Sociedad at the moment they are indeed a dark horse club which is indeed very good even they can get the top position defeating Inter, Benfica and Salzburg who are subscriptions and I think being in the round of 16 with group winner status for a debutant club is quite impressive for Sociedad.
It is indeed very difficult to predict which one will be superior in the Inter Milan vs Atletico Madrid match. Because each of these teams has quite consistent performance in their respective domestic leagues. It's just that Inter Milan is currently better than last season. In fact, currently Inter Milan is also leading the standings in Serie A quite well. Meanwhile, Atletico Madrid is currently still struggling in the top 5 and 4 in Laliga. But still, Atletico Madrid's strength cannot be underestimated because Atletico Madrid is even stronger than Real Sociedad in Laliga based on the current standings in Laliga. So Inter Milan will also certainly have difficulties when facing Atletico Madrid.
Meanwhile, Real Sociedad seems unlucky in the last 16 because they have to face PSG in the last 16. Even though PSG didn't perform well enough in the group stage, PSG is still one of the clubs whose strength must always be taken into account. Because the depth of the PSG squad is also quite superior to Real Sociedad. And the Real Sociedad vs PSG match is equally difficult to predict.