The suit is definitely part of it! Even the additional make-up to further exaggerate his face "X". It is kinda subtle, but the mature/adult features are excellently done by BOCHI. It seems like Xeno and Stanley are still in their early 20's but that's still potentially a decade of experience with most of it being at a professional level. Ah, so the "air" of confidence is probably another huge aspect of this.
Yup, all of us agree that Taiju really needs his time to shine. I love the almost excessive overemphasis on it "just not being right" to shoot machine guns at people. Taiju is just driven by his morals.
Back to the blind Oda faith (until the next B.S. of course).