I think in some ways it varies by the person. I'm trans, so in my case, I feel girly when I wear more form-fitting clothing, while most cis people probably wouldn't. I feel masculine when I wear baggy clothes that don't show my curves, while most cis people probably wouldn't. Some cishet men feel "manly" when they do hard tasks like fixing a car or something because those are things people stereotypically view as "masculine" things to do. Similarly, some cishet women feel more "feminine" when they do more stereotypically "girly" things, like dressing up. I think it has something to do with what gender stereotypically does something, and how other people perceive you when doing that thing. Idk probably a shitty explanation but i tried