Using: Send Customized Data via HTTP Request (Advanced)
Following this guide:
How do I get the exact output thatan Audience Connector Webhook is sending to my site via a POST?
1. You can use Trace. If you click on the entry in the trace that shows Actions Processed, it gives you all the detail of the variables, templates and then the actual payload sent, see screenshots below.
2. You could use something like webhook.site temporarily, for test users. There, you can create a temporary endpoint. If you change your webhook's url to that (again just for test users), it will show you exactly what was received.