Is nvarchar 0-indexed? Is the max length configuration for nvarchar 0-indexed, e.g. If I declare column x as type nvarchar and set the max length to (2): (X nvarchar(2)) does that mean that the column takes 3 nvarchars? or only 2?
This is quite clearly explained in the documentation. The value in parentheses indicates the string length. So nvarchar(2) has a string length of 2.

https://msdn.microsoft.com/en-gb/library/ms186939.aspx


  nvarchar [ ( n | max ) ]  Variable-length Unicode string data. n
  defines the string length and can be a value from 1 through 4,000.