Maybe Quinto's "no stress" comment means he feels confident that he turned in a really good performance and that it will be a really good movie.
A few weeks ago Quinto made a similarly calm and detached statement, and there was frantic speculation that he was unhappy with the role/the production, that he didn't care any more, and that he wouldn't be returning to Star Trek. I'm inclined to think Captrek
is probably right, and that Quinto does have a lot of confidence in his performance and in the production, and that he isn't overly stressed about it at this point.
Either that, or he's just really good at compartmentalizing.