password managers in the browser still store them encrypted. They usually authenticate via a passkey, in-built security in the OS like windows hello, or through other services such as SSO through google; That said, if you have them on auto-pilot with this authentication, anyone with access to the device can theoretically access them, though to actually view them in the password manager they usually require you to authenticate.

Browser password managers are sorta less secure than a third party one, assuming you turn on all the convenience features to make your life easier, but a lot of third-party password managers have the same convenience features a lot of the time anyways.