Creating new Zen component

I’m trying out Drupal theme in D7 and after reading some posts about responsive, recommended Drupal themes, I installed the latest Xen for Drupal 7.
I’m a little familiar with SASS and got my gulp running, and don’t see much docs of the recent versions. Due to streaming issues, I haven’t been able to get through the latest John Albin video which is three years old.

I created a sub-theme through Drush and copied some of the template files from the parent theme.

My first Q is it normal for this D7 theme to have .twig files alongside the .scss files?

If I want to create different regions that don’t seem to be supported by the /sass/components directory, should I re-use or duplicate a similar component and create my own component SASS component files?

What pointers, specific to Drupal theming, will help me grasp how to exploit the work done by the creators? thx, sa

Drupal version: 


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