Microsoft has very little documentation on their .iqy (or a Excel Web Query - Internet Inquiry) file and nothing about their allowed options or format. This because the .iqy file is normally created from a VBA Web Query output. But, if you reference the VBA QueryTable documentation instead and do some translation, you'll find this (simplified here):
Note: There are other .iqy options like SharePointApplication
but aren't prefixed with "Web" and therefore weren't added to this list. You can find the rest of them under Properties.
An example Web .iqy file is formatted in this style:
WEB
1
https://www.example.com/file.csv
Selection=1
Formatting=None
PreFormattedTextToColumns=True
ConsecutiveDelimitersAsOne=True
SingleBlockTextImport=False
DisableDateRecognition=False
DisableRedirections=False