Reference: https://msdn.microsoft.com/en-us/library/ee691831.aspx

Reference for the difference between VBA7 and Win64 flags:

To ensure backward compatibility with previous versions of Microsoft Office, you use the VBA7 constant (this is the more typical case) to prevent 64-bit code from being used in the earlier version of Microsoft Office. For code that is different between the 32-bit version and the 64-bit version, such as calling a math API which uses LongLong for its 64-bit version and Long for its 32-bit version, you use the Win64 constant. The following code demonstrates the use of these two constants.

To summarize, if you write 64-bit code and intend to use it in previous versions of Microsoft Office, you will want to use the VBA7 conditional compilation constant. However, if you write 32-bit code in Office 2010, that code works as is in previous versions of Microsoft Office without the need for the compilation constant. If you want to ensure that you are using 32-bit statements for 32-bit versions and 64-bit statements for 64-bit versions, your best option is to use the Win64 conditional compilation constant.