Content Modifier Header

Hi everyone

With the content modifier, I can create variables in the Header, Exchange Property, and Message Body:

However I have the following Question:

1. What is the differece or When should I create variable in the Header and Exchange Property?

2. In most blogs that I have found on the internet, the data types appear as java.lang.String . What other types of data can be handled in the field "Data Type"?

3. I am creating a variable in the property for get the process execution date. I am using ${date:now:yyyy-mm-dd'T'hh:MM:ss'Z'}, but How can get the date in this format 2022/04/28 or 2022-04-28

Regards