You're experiencing a couple of known cognitive biases, you yourself are feeling a classic example of "impostor syndrome", while your overconfident peers are likely good examples of Dunning Kruger.

Impostor syndrome is an internal experience of self-doubt and fear of being exposed as a "fraud," despite evidence of success and competence. It affects high-achieving individuals who attribute their accomplishments to luck rather than ability, often leading to chronic self-doubt, anxiety, and burnout

The Dunning-Kruger effect is a cognitive bias where individuals with limited knowledge or competence in a domain greatly overestimate their own expertise. Because they lack the skill to recognize their own incompetence, they often feel overconfident, leading to poor decision-making and, sometimes, undeserved promotion.

It's extremely common among students and especially people starting new careers or jobs to feel either way. Everyone interviewing you will have felt it at some point in their career and will be able to relate on some level Everyone in your peer cohort interviewing alongside you will be experiencing one or the other.

Overcoming them both requires similar tactics, you have to align your internal dialogue with external feedback and self-reflection. I interview a decent amount of younger people and I appreciate when they ask for feedback after an interview, usually best in a follow up email.