How can I define Wix properties and values that change depending on which Visual Studio configuration is active? e.g. For our release build, var x = 1 and for the export build,
You can use Project Reference Variables for that. No need to specify constants.
Sample steps:
Right Click 'References', 'Add References'
$(var.ProjectName.Configuration)
Resources:
Complete list of Candle preprocessor variables
Using Project references and variables