Ok, many thanks for the graphic explanation. I understand now that launching Wipe Free space from the different menus does different things. It may be useful for the software developers to remove the ambiguity. Specifically:
(1) When wiping free space in the CustomClean/advanced/WipeFreeSpace, it will or will not wipe MFT free space depending on the setting in Options/Settings MFT checkbox. However, will it also follow the settings in Options/Settings for the other choices (normal/secure, number of passes, alternate data streams, cluster tips)?
(2) When wiping free space in Tools/DriveWiper, it will automatically wipe MFT free space. But, will it wipe also alternate data streams and cluster tips? How many passes? Normal or secure?
It's unfortunate that there is no detailed user manual for this product. However, this seems to be the norm in the software industry. The company that owns this product also sells Avast antivirus products, which I also use. However, there is no detailed user manual for this product either. Perhaps the software developers will clear up the ambiguity with the wipe free space issue in the user interface. I'm sure 99% of people using this product have no idea about this, and click options without knowing the details of their wiping operation that they selected. Maybe someone will also write a detailed user manual. It will be a good reference guide, and only needs to be written once.
Thanks again for your patience.