If you choose the option passcode, the code will be embedded in the meeting link, meaning that if you enter the meeting using the link you will not have to enter the passcode. However, if you join a meeting from the join button in Zoom using the meeting ID you will have to enter the passcode.
If you do not check the checkbox for passcode or waiting room when you schedule a meeting a waiting room will be assigned by default.
If you already have meetings scheduled without a passcode or a waiting room that occurs after 27 September, a waiting room will be added automatically if no other action is taken. If you edit your meeting and add a passcode instead you need to resend the invitation link.
For more information see: https://support.zoom.us/hc/en-us/articles/360045009111