Which Whatsapp trigger i need to use (click a link OR send a message)

I want to publish the ManyChat inside Whatsapp, where i will have 3 options for the users to interact:-

1. either directly message the number on whatsapp application
2. scan QR code
3. click on an image inside our web site

now we have those options for the trigger:-

 

so not sure which one i need to use and why to achieve the 3 options? Thanks