HI ALL

I’ve a site (basically a landing page) with just 1 button → a whatsapp ref url:

user can click the whatsapp ref url and pay for the coaching service directly in Whatsapp.

Question

1. in terms of META ADS, what is better to do? 
   a) sales camp that land on the site?
   b) sales camp that land on the whatsapp ref url? (in the first automation the service is explanied inside whatsapp)
2. I set up Conversion API in Manychat, do I need set up conversion API for the site too? (with Stape or similar tool). Both of them are better or not?

THANKS IN ADVANCE!