I don't think someone who tends to follow traditional gender roles should be considered sexist, especially since we know he doesn't view that as the 'right way'. Traditional is a better term. Sexist is more about prejudice, and despite his delicate things line, he is very comfortable with the thought of women fighting with swords in both fantasy and real-life.
As for the questions on language, low key isn't really used as a little. It's meant to mean restained or showing less emotion. Like saying 'I low-key want to eat a cake' casually, without putting much emotion into your voice. I hope that made sense. But yeah, saying he is low-key sexist does not mean a little sexist, just that he is sexist. Maybe less vocal is all. And again, think sexist is the wrong term here as well.
I normally use stupid. Little fun fact, Americans vary greatly, and how we talk will depend on where we were raised state-wise and maybe even city wise. I do normally say stupid rather than not great, and also indicate someone should die because they can never do anything correctly for the love of- XD Yeah, no worries.
Also, yes, I wonder when we will get an update on the castles he's making. That will have to wait, though, because he is making a video on Wonder Woman 1984 and the fact WW basically raped a guy. XD That is going to be a hilarious video.