2 Where Claues with 1 Sub query using NOT IN notation

Select CompanyName  From Customers
Where Country='usa' 
and Region NOT IN (Select Region From Employees
   Where Region IS NOT NULL )
Order By CompanyName;

--OR better to use not exists
Select CompanyName  From Customers c
Where Country='usa' 
AND Not Exists (select 1 From Employees e Where c.Region=e.Region)
Order By CompanyName;