Some few questions...

1 - what is the difference betwen scan "open" or "executed" files?
2 - and can my PC be infected with a found virus during a .rar extraction?

 

Scan on open would be opening a word document or rar/zip file - while execute would only mean for program files, and executables - ie, a document such as a Word doc/docx or Excel sheet would not trigger execute, as they are not executed - they are opened.

A rar/zip encrypted virus/trojan can infect you only when extracted *AND* executed... otherwise these infections would sit waiting to be triggered before they could infect you.

hth