Where is the primary place to configure my layout?

Hi there,

Most of the options are in the customizer:
https://docs.generatepress.com/article/finding-the-customizer/

Then you should see each category such as Layout, Colors, Typography etc.

If you search for Overview in our documentation it should provide some simple guild lines of our features:
https://docs.generatepress.com/

Let me know if you need help finding specific features :)

So, if I want to have a post container with full width.
I should go to the Customizer -> Layout -> Container or I should go to the Elements and create Layout (because I realize I can do that by creating a Layout in Elements and set container is full width)?

If you only want the single post container to be full width then the Element module is the way to go :)

I have done that, but I'm facing a problem.
How can I set padding properties for the full-width container that I created on Elements?

I'm not sure what you mean.

Full width means full width so all padding is removed, otherwise it wouldn't be full width.

It might be easier if you can link me to an example you are trying to create so I can do my best and point you to the right direction.

Yes,

I'm trying to make a theme copy of this page https://www.gamingscan.com/ and this is my page https://thomaykhoua.com/ at now.

Could you please show me the steps?

Thank you.

Which part specifically?

The hero image part can be achieved with Page Hero in Header Elements:
https://docs.generatepress.com/article/header-element-overview/

Then the blog columns can be done with the customizer options:
https://docs.generatepress.com/article/blog-overview/