How to manage the ECID, For example a new user came to website and anonymously started booking form based target implementation while using edge server and we want to show as per geo location some picture and some messages to an anonymous customer feel free to provide approach
First you need to understand your requirement, define your audiences and create activity.
In your scenario, New visits is one audience and Geo locations are other and also if you want to define as per customer details.
Example: If you want to target US new visitors then
In Activities, create activity Experience Targeting (XT), change audience from All visitors to US New visitors, display pictures or message as per geo selection and define your goal and settings.