I know for a fact that the Apple IIGS version of KQ4 was the rare AGI version.
The reason I know this is because it’s the last Sierra game I was able to play on my home computer, the Apple IIGS, before Sierra killed development for the platform.
As a kid I often wondered why my version of King’s Quest IV didn’t look the same as the photos in the Sierra Catalog.
Therefore, if you want to play the AGI version of KQ4, seek out an Apple IIGS emulator and download the abandon-ware IIGS KQ4 disk images.
You’ll also benefit from the best sound quality possible at the time, since IIGS audio killed just about any other home computer stock audio using its special Ensoniq chip.
Check out my post about dropping IIGS support in the “Ask Ken Williams” section, as I posted up a question a handful of days ago on a similar topic.