I was comparing scans of the "Premiere" Edition of HQ for Quest 3 (Prince Magnus' Gold) to the NA version and this one wasn't quite as interesting as from
the Lair of the Orc Warlord.
The EU version gives 200 gold coins as a reward for completing the mission, while the NA version gives 240.
Mostly the original version was sparse in terms of furniture placement and had fewer monsters. One interesting bit from the original non-US version was this:
"IF any character decides to keep Prince Magnus' gold instead of returning it, he will be outlawed. This character may never become a Champion."
[That's 250 gold per chest, for a total of 750 gold! But that means you forfeit the "reward" for becoming a Champion which in the original edition was 500 gold after completing only three quests. Plus you got to put a little "champion" sticker on your character sheet that resembled the winged rod of Asclepius.]
The EU version in general (which was based off the Premiere Edition) doesn't assume the Heroes will work together. You can cast offensive spells on each other and attack each other, while this is much harder to do in the NA version, so this bit makes sense.
While the US version clearly says that the Heroes cannot keep any of the Treasure inside the chests.
Any other interesting variants you've found between the EU and NA versions of quests? I see NA's "The Lost Wizard" is called "The Stone Hunter" in the EU edition (where "Wardoz" becomes "Kalern"). And in "The Fire Mage" the bad guy gets the three Fire Spells (so you can't even choose them, nerfing one of your magic users) while the NA version gives him a stack of Chaos Spells AND makes him immune to your Fire (and gives him more body points, of course).