Okay I've played the current build all the way through 3 times at this point, and something I've pieced together is that Argos/Nikos seems to speak or at least understand English. From completing Khenbish's route I learned the hotel often has trouble translating wordplay. Nikos contacts Asterion using Greek but "nose" the memes he forwards to you well enough to quote them later on depending on the choices you make. If you have Khenbish on staff Nikos has a cute scene with him where Khenbish is cooking saganaki for him and Nikos tries to break the tension by saying "cheesed to meet you..." which just confuses the boar. Now I don't know Greek but I doubt that pun works in both languages, so it seems at that point Nikos is speaking English. So yeah, I think Argos is bilingual but primarily speaks English for whatever reason.
I'm also with the MC on not understanding how or why a snake man who directly works for a Greek god is Christian. I'm pretty sure snakes are viewed as inherently evil in most Abrahamic religions. Then again, Nikos often talks about how snakes are meant to be deceptive, maybe it's some kind of guilt complex.
Also, I think in my latest playthrough the MC hugged Nikos like... 5 times? And the description of him drinking water after his near miss with the Effigy is oddly cute. Makes me feel nostalgic for when I was a child and my dad would have me hold his Burmese python whenever he cleaned out his habitat. That snake was so docile, I was never afraid of being bitten or strangled by him.