MacOS – How to create bootable flash drive from macOS High Sierra combo update

The short answer is that there is no difference to the end result. The difference lies in the process.

As an example, your current USB installer will install macOS Sierra 10.12.0. After installation you will still need to update it via the Mac App Store to get it back to macOS Sierra 10.12.5.

If you erase and install from the internet the version installed will already be macOS Sierra 10.12.5.

You can also startup from macOS Recovery and may be able to install macOS Sierra again without the need to re-download it.

But to answer your question, whatever you do makes no difference to the end result. In this case you just have a number of roads all leading to Rome.

This can be done by console for Windows 10 iso images (Not sure about 8/7, but leave any comment if it worked for you).
Start connecting your usb drive and type diskutil list to display all connected drives.
You'll see something like:

/dev/disk0 (internal):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                         500.3 GB   disk0
   1:                        EFI EFI                     314.6 MB   disk0s1
   2:                 Apple_APFS Container disk1         500.0 GB   disk0s2

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +500.0 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume Macintosh HD            185.7 GB   disk1s1
   2:                APFS Volume Preboot                 47.1 MB    disk1s2
   3:                APFS Volume Recovery                512.8 MB   disk1s3
   4:                APFS Volume VM                      4.3 GB     disk1s4

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *15.6 GB    disk2
   1:                 DOS_FAT_32 LALA                    15.6 GB    disk2s1

For my case, the usb drive was /dev/disk2. Knowing this, format your usb drive with:

diskutil eraseDisk MS-DOS "WINDOWS10" MBR disk2

where disk2 is the usb drive id known in the prior command and "WINDOWS10" is the volume label (to be used later).
Please double check this step, or you could delete all data in another drive.
Then mount your image with:

hdiutil mount your_windows_10_image.iso

the command will return the location of the mounted iso

/dev/disk3                                      /Volumes/CPRA_X64FREV_ES-MX_DV5

so finally copy all the files from the mounted iso to your usb drive:

cp -rpv /Volumes/CPRA_X64FREV_ES-MX_DV5/* /Volumes/WINDOWS10