This was going to be my post. KQ1 and QfG2 are pretty much recreations of the original games with better graphics and a mouse-based interface. KQ1 is pretty simple by modern standards and I’d recommend mostly for nostalgia value or “historic” interest, but I think QfG2 holds up very well.
The AGD version of KQ2 is significantly different from the original and is longer, has a more complex plot, new puzzles, and different solutions to some of the old puzzles.
No, there are a few Easter Eggs but in terms of story and puzzles it is the same as the original game. Well, the official Sierra 1990 remake of the game, at least. I think there may have been some minor changes between the 1984 version and the 1990 EGA version, but I only played the latter.