insouciant
adjective·/ɪnˈsuː.si.ənt/
Casually unconcerned; marked by an easy nonchalance that can read as charm, indifference, or quiet defiance (often slightly French in flavor). Where carefree is innocent, insouciant can be cultivated, a refusal to be pressed.
He answered the accusation with an insouciant shrug, as if consequences were a rumor that couldn’t reach him.
Etymology
From French insouciant “unconcerned,” from in- “not” + souci “care, worry.” The word’s elegance is part of its meaning: unconcern worn lightly.
Related Words
nonchalantclose near-synonym; often interchangeable
sangfroidcoolness under pressure; more specific
languidrelaxed; can overlap in pose, not in attitude
sprezzaturastudied effortlessness; later in your list, a conceptual cousin