Is the cast operator is intended to return two characters or up to two
characters?
How can I change it so it will return 02 instead of just 2?

According the help file DT_WSTR is A null-terminated Unicode character
string with a maximum length of 4000 characters. So what does the ",2"
do?

Would you recommend that I use
Convert.ToString(DATEPART("dd",GETDATE()) instead of the cast?
Why is one preferred over the other?
Does the Convert.ToString create unicode strings?