Using the form Back Office
For example I want the product 4 uses a specific .tpl is "test.tpl"
So then choose Product ID 4 and then in my déroulan I select my dwt "test.tpl"
Using native module
You have in any case need to use the module configuration, but you need only create an additional .tpl in your theme folder which would be for a specific product_4.tpl .tpl for the product ID 4