How to access to System Files with Spotlight ?

Go to the menu File>New Smart Folder

Add a new condition with the + button.

In the Kind field, choose Other and select "System Files".

Now you can include all system files in your search queries !

How to add grouped conditions with All, Any or None ?

It's simple. Before to click on the add button, press the "alt" key on your keyboard.
The "+" becomes a "...".

Now you can play with all conditions...