What should be WordPress themes

Hello themeforest autors and moderators)
In current time i want build WooCoomerce theme, but i run into an some questions:

  1. How i anderstand themes must work without any plugins. If i wish ctreate some diferent versions blog-archive how i need realize this - from plagin or defult customaizer?
  2. where must be templates files: in plagin or in theme?
  3. Plagin neded for create a custom post types. where i need create css for it?

p.s. I got acquainted with the requirements of Themeforest
If you want to send me to re-read them, please specify the article and the number of the requirement.