WHAT EXACTLY DOES THE ADVENTURE PACK ADD TO IWD2? IS IT WORTH GETTING FROM GOG BECAUSE OF THIS ADVENTURE PACK EVEN THOUGH I HAVE A HARD COPY AT HOME?

I IWILL USE MY CAPS LOCK WHEN I FEEL LIKE USING MY CAPS LOCK. I HAVE FOUND THE ACTUAL SOLUTION HERE:

Regarding Icewind Dale II, GOG lists the Adventure Pack as included, whereas the Impulse version does not.
That's not exactly true. ALL versions of Icewind Dale II contained the contents of the adventure pack - which are just 11 bonus items (10 of which have heart of fury alternatives) sold by two merchants. Even in the unpatched release version of the standard version of the game only required you to either:

Placing a 1k overide file in the override directory

or

Changing a variable in the console


Oh and the final patch added the items in to all versions of the game. The only item that was left out was the Avarine Decanter (the only one that didn't even have a Heart of Fury mode alternate version). The override or console command will still spawn the item in a shop inventory in the "Wandering villager" who sells it though. Nym is that merchant in the wandering village and he's in the base game too as a merchant and important plot NPC; the variable does in-fact only add the item to his shop inventory rather than control whether he appears or not as it did with the BG2 bonus merchants.

It's really disingenuous to advertise the game as containing the "adventure pack" which only differs from the patched vanilla version by a single item; not even that, it only varries by whether the variable enable the item in a briefly accessible NPC merchant who sells it is set to spawn by default or not.

Of course I can't really blame GoG for that one - there was almost no documentation on what the "adventure pack" added even before the official patch turned all the useful content from it on - content that was present in all the installations already but merely suppressed by disabling the 2 merchants in the initial release version. I doubt the realize themselves that the sole remaining "bonus" content is the Avarine Decanter. Black Isle's choice in naming the bonus content for that was… questionable. "Adventure Pack" = a bottle as of 2.01 patch.

http://www.sorcerers.net/Games/IWD2/index_mods.php
-First item on the page explains it; you can either use the 1k override (changes that one global on startup) or use the console command to tell the game to spawn the NPC who sells the only bonus item not added by the official path vanilla game. In all cases besides simply cheating the lone missing bottle can only be purchased during a brief portion of the game assuming you have the gold though as the wandering villager Nym only spawns during a short portion of the game. It is also the least useful of the formerly bonus items and was probably left out of the patch because most people who had the collector's edition w bonus pack never used it in the first place.

Now the whole reason the avarine decanter is useless in the patched version is because what it does is spawn a Genie NPC merchant - who can be summoned 3 times before he just goes bezerk and attacks you. While he does sell some really great items - these items are purchaseable shortly thereafter from the "Tower Merchant" who does not require you to buy the right to buy from him. Again - probably was intentionally left out of the patch since the items you could buy from him were simply added to a more normal store and because there were a few known bugs that could happen as a result of using the decanter at certain times and in certain places. In my original collector's edition copy of the game I used it somewhere I think the game decided I should not have and my saves in that area were rendered corrupt.

This potential can be avoided without losing access to the real items the genie in the bottle sells you but just not installing the "pack" that spawns Nym. I did experience this issue even after the patch - the decanter was not fixed by it - although they bypassed the issue in all versions by simply adding his items to a later normal-ish store. As the final patch did not remove the decanter from games it was active in - nor did it prevent people from changing the variable in non-collector versions - I would suggest simply avoiding the problem and not getting the decanter that spawns 3-use shopkeeper but instead just buying the items for a lower total cost in the normal stores they added them into for "Adventure Pack" and non "adventure pack" users alike.

This was probably one of the least impressive pre-order or collector bonuses I can personally remember - and it would have been just as much of a joke even if it hadn't been so easy to enable with a console command.