Reading previous posts, the following could be concluded:

1. The pictures in the game store are of the floppy version.

2. Many users were requesting the enhanced CD version with better portrait graphics and voice acting.

3. A couple of users explained that using ScummVM you can choose between the DOS and Windows versions.

However:

1. I bought the King's Quest 4+5+6 pack just now and the version starting from GOG is the enhanced version.

2. Both DOS and Windows versions are the enhanced version.

3. Running in Windowed mode, the window info states that it is the CD version.

Explanations:

1. The original version is the floppy (DOS) version.

2. The enhanced version is the CD (DOS/Windows) version. This is the version that will run when executed.

However:

The original floppy version's pixelated graphics can be unlocked by editing the kq6.ini file, located in your KQ6 game folder (on my computer it's located in C:/Program (x86)/GOG Galaxy/Games/Kings Quest 6/kq6.ini).

Find the line that says: enable_high_resolution_graphics=true

Change "true" to "false" (without the quotation marks).

Save the file. Start the game.

Done. You've now downgraded KQ6 to its original pixelated goodness. :)

I also greatly prefer the low-res graphics.

You can also get the original/low-res graphics using SCUMMVM:

1) Use the DOS version of the game
2) In the SCUMMVM settings, select "edit game" and untick the "high resolution graphics" option.
3) Enjoy!

Didn't know that! Thanks!

The original release of this game in 1992 was the floppy version. The version copyrighted 1993 is the CD version, which had the voice acting and the higher res portraits.

The CD also included a DOS version with the original portraits and voice acting.

Yes, there is only one version of King's Quest 6 CD and it includes everything.

The hires portraits were exclusive to the Windows 3.11 SCI interpreter, which is a nightmare to run nowadays.
And the Windows 3.11 interpreter also ran the game in hires mode.
The hires portraits are inside the folder called ACTORS.

These hires portraits were literally hacked into the SCI interpreter. Like there is one kernel call and control is passed to a Windows 3.11 DLL to handle all the portrait stuff, which includes drawing and playing back the audio and it will only return control to SCI after the sequence was completed.

The lowres portraits were used by the DOS interpreter.
The game scripts literally check if they are running "under DOS" or "under Windows" and switch between these.

Both of these played audio, but also had subtitles.

BUT King's Quest 6 CD did not support voices + subtitles at the same time. This feature was patched in through ScummVM. In fact most of the game supported it already, there were only some instances that didn't work properly, which is probably the reason why it wasn't enabled by Sierra back in the days. I guess there was not enough time.

Another fun fact: the lip syncing between lowres and hires portraits is not even the same. Different resources are used. And if I remember correctly, there are some instances where there is no lip sync data for hires portraits, and some other instances where there is no lip sync data for the low res portraits.

For low res portraits the game uses some kind of babble mode when that happens. The characters will just open and close their mouth randomly.

Originally there was an idea to create hires lip sync data out of low res lip sync data and vice versa. Theoretically that would be possible, and that would make these few scenes finally get lip sync'd. This feature was never implemented. It's very weird that some of that data is missing.