Configure elements for code generation

My question relates to code generation for Language = C with the Embedded Coder

1. Is it correct, that the option's Configuration Parameters > Code Generation > Interface > Code interface packaging main impact is the function interface? With Nonreusable function meaning void-void interface; and Reusable function meaning the model data being passed to the functions according to question 2)?
2. Additionally to the option from question 1), only for Reusable function, the option Pass root-level I/O determines whether to pass the argument(s) individually or by structure references, right?
3. Additionally to the global options from 1) and 2), Code Interface > Individual Element Code Mappings gives access to configure function prototype and arguments in detail, is that correct?
4. Defaults for 3) can be configured in Code Interface > Default Code Mappings?
5. What's the purpose of the Code Mappings Editor, compared to the options from 1) and 2)? Is it only a newer way of doing the configuration (that's how I interprete the migration guide)? Or is it rather a mean for configuring single elements like inport, parameter, signal, ...?
6. Last, but not least: If it's possible to configure signals and parameters in 5), are Simulink.Signal and Simulink.Parameter objects still needed?

Sorry for being a little confused... And thanks in advance!