Over the years there seem to have been a ridiculous number of different editions of NWN. Including Gold, Platinum Diamond and now Enhanced. I have the Diamond on GoG (and the discs for the Gold somewhere). Is there any significant improvements or additional content in the EE above widescreen support and patched multiplayer to make it worth getting? I can easily use the patches for widescreen that exist and there are workarounds for multiplayer, if I ever used it.

I have both. I was very underwhelmed by EE.

If Diamond works well for you now, there is no reason to get EE, unless you want to play multiplayer with people who are using EE.

The changes are superficial. The graphics enhancements, don't actually fit in well with the game engine, and are just post processing effects, most of which you could add with 3rd party tools, or the NVidia driver effects.

I had to disable them because they killed performance on my machine, but when they were on, I was NOT impressed.

The main attraction was definitely the multiplayer fixes. There are graphical improvements and some paid DLC.

The only thing you'll likely notice in single player are the graphics. They have dramatically improved how light works in the game and it looks much nicer. But that about it.

Here's a fantastic document that lays out all of the changes.

https://www.beamdog.com/files/release_notes/nwnee_release_notes_final.pdf

I have both editions and almost exclusively use the EE now, but as the others said, changes in single player aren't that significant. The main reason I got it (on sale) is for the enhanced edition of Darkness Over Daggerford (and later Tyrants of the Moonsea), both of which I had already played in their previous free versions for Diamond, and yet I thought these enhanced editions were really worth it. They are expanded, use new tilesets, voiceovers, music, even feature some new and exclusive creature models in the case of Tyrants. And I wanted to support the re-release of the previous premium modules Pirates of the Sword Coast, Wyvern Crown of Cormyr and Infinite Dungeons, which aren't officially available for Diamond anymore (only as "Abandonware").

I'm quite invested in the NWN community and like playing new community modules - which are few and far between these days but more likely to be EE exclusive now. The better multiplayer support is definitely a plus, too, and there are some improvements with regard to the use of custom content (which is now stored in the Documents folder, separately from the installation folder, just like in NWN2; also, using patch haks to manage override files works better now, and there are other advantages that you only notice when you're into this sort of thing, like, you can now have up to 255 override heads per race during character creation already, which wasn't possible in Diamond).

The downsides are that the EE introduced a few new bugs/performance issues (of which I've only experienced two so far myself - a serious drop in performance due to the sparkle effect on pixie and faerie dragon familiars, which can be fixed with a community override; and some door transitions behaving oddly occasionally), and some older community modules have new "bugs" because of it, too (e.g. interactive placeables embedded in walls slightly shifted their position and are no longer reachable in some cases, or very rarely, some scripts don't seem to trigger anymore.)

If you don't play NWN a lot, and you're mostly just interested in single player, be it the official campaigns or old legacy modules, and you don't care a lot about modding the game, then Diamond would be absolutely sufficient. If you're an NWN enthusiast, it can't hurt to have both editions, just lower your expectations a bit. There are a lot of changes and improvements, but most of them are "under the hood" and not really relevant and visible to the average (single) player, sadly. Interesting, I didn't know about this yet. Quite handy to have, thanks!

Thanks for all the helpful answers. So from my point of view the main improvement is that under Windows it finally puts the user data under Documents, but seeing as I always put games under C:\Games anyways that's not essential. Although if I cant find my backups of the premium modules I might be tempted. And I've used SweetFX for other games, so sounds like I dont need the graphical improvements

Does the CEP work with it? IIRC a lot of modules used that.

The advantage of that has less to do with accessibility of the user data (I assume your comment was referring to possible issues with Window's Programs folder?), it's more that user data is separated from the installation. For example, you can uninstall the game without having to backup all the user data and custom content before that, because it stays in Documents. For Diamond, it doesn't really matter, but for the EE, GOG often just updated the offline installers instead of providing patches for new versions, which meant re-installing the game with each new patch. That would have been much more of a hassle if all custom data would have been deleted along with the installation folder. And I guess another idea is that you don't accidentally mess up the files required for the game to run. Yes.

ik this is an old post but in case anyone is looking this up and wants details vs the two

Neverwinter Nights: Enhanced Edition and Neverwinter Nights: Diamond Edition are both versions of the same classic RPG, but they differ in several key aspects:

Neverwinter Nights: Diamond Edition
Content:

Includes the original game.
Contains the two official expansions: Shadows of Undrentide and Hordes of the Underdark.
Comes with three premium modules: Kingmaker, ShadowGuard, and Witch’s Wake.
Graphics and Interface:

Uses the original graphics engine from 2002, which can look dated by modern standards.
The interface and controls are the same as they were at the time of the original release.
Compatibility:

May require compatibility tweaks to run smoothly on modern operating systems.
Supports community mods and custom content, though some newer mods may be optimized for the Enhanced Edition.
Neverwinter Nights: Enhanced Edition
Content:

Includes everything from the Diamond Edition (original game, expansions, and premium modules).
Additional premium modules available for purchase.
Graphics and Interface:

Improved graphics with support for resolutions up to 4K.
Enhanced lighting and shaders.
The user interface has been modernized for better usability and accessibility.
Compatibility:

Fully compatible with modern operating systems (Windows, macOS, Linux).
Seamless integration with Steam Workshop for easier access to mods and custom content.
Cross-platform multiplayer support.
Additional Features:

Includes bug fixes and quality of life improvements not present in the Diamond Edition.
Improved toolset for creating custom modules and content.
Key Differences
Graphics and Performance: The Enhanced Edition features improved graphics and better performance on modern systems.
Compatibility: Enhanced Edition is optimized for modern operating systems and hardware, reducing the need for compatibility tweaks.
User Interface: The Enhanced Edition has an updated UI, making it more user-friendly.
Community and Mod Support: Enhanced Edition integrates with Steam Workshop, simplifying modding and custom content.
Conclusion
Choose Diamond Edition if you prefer the classic experience and don't mind dealing with potential compatibility issues or outdated graphics.
Choose Enhanced Edition if you want improved graphics, better performance, modern UI, and easier access to mods and multiplayer features.

I will add that there are still patches being made for the game. There are a veritable TON of new features for builders wanting to make customized persistent world servers.
The biggest being NWSync, which allows servers automatically to download the hak data for you. No need to go hunting the Vault or the PWs website for the hak files so you can join their server, it's all automatic and deduplicates art assets (if you got that fancy new PBR Cave tileset from Bob's PW server, and you go to Frank's PW server and he uses the same fancy new PBR Cave tileset, you only need the one set of files). Unlike haks that may contain the same assets in three different haks by three different author.

The new Curated section means you can just choose some of the top modules from a list, click a button, and everything is installed for you.