What is the true impact of Panels Everywhere on theming and layout duties? From an answer on another question: 


  If you have chosen Precision because it is minimalist, then you might
  want to consider adding the 'Panels Everywhere' module. This module
  works very well with Panels (same authors) and allows you to bypass
  the Drupal Theming process altogether. This greatly simplified my
  styling work.



Does this mean regions and blocks are completely ignored with Panels Everywhere (PE) in favor of panels only?
If so, does it mean one has to recreate some layout for standard pages such as node edition and publishing for example? I have an editor user profile to create specific content. Do I loose all the layout of existing Drupal screens the user could access?
After enabling PE, what configuration is expected regarding layout and theming (CSS) on standard pages delivered by Drupal?


Fact is, when trying PE with the Precision theme, I lost layout on all standard pages, but I want to know if this is a configuration issue or not.
From my own findings:


Yes. In fact, one can set a site template which (more or less) replaces the concept of regions.
No, one should set a site template and not forget to have a Page Content pane.
None, except for the site template itself. Eventually, some can be set on the Page Content too.