invoice type

The invoice type to use is determined at the order type level, if you need / want different logic, you'd need to write your own code and invoke your own logic for that.

I have a type of invoice depending on the type of country, with code you can specify the country in the numbering but I cannot find the variable that stores the type of invoice

There is an invoice type setting configurable at the order type level (See the screenshot below):

Automatically closed - issue fixed for 2 weeks with no activity.