Passkeys rely on you holding a private key. The initial design was that a device (like a browser or computer/phone) stored the private key in a TPM-protected manner, but you can also store it in a password manager.
This is more secure than a password because of the way private/public key encryption works. Your device receives a challenge encrypted with the public key, decrypts with the private key and then responds. The private key is never revealed, so if attackers get the public key they can’t do shit with it.
Just be sure that your private key is safe (use a strong master password for your PM vault) and your passkey can’t be stolen by hacking of a website.
Capybara