Neverwinter Nights/Version differences

If you're playing the original campaign, there are two main categories: Unpatched (version 1.11 seems to be the one that everyone owns), and Diamond (i.e. a version with all expansions installed). For obvious reasons, playing the expansion campaigns can only be done on Diamond.

Unpatched

Several glitches are only possible on unpatched Neverwinter Nights, or work better without patches. In particular, you can skip the golems in the Creator Race Ruins Past because they're missing several important immunities. However, this is not a huge advantage: in the current any% route, the places where unpatched gets a large time advantage are mostly not on the route anyway (not even on the unpatched route).

Unpatched games do not have an Appraise skill. This makes prices more consistent; Diamond can get lower prices than unpatched, but only with luck. So for a single-segment run, unpatched gives you less chance of losing a lot of time through bad luck.

The most notable feature of unpatched, though, is a bug in speed stacking. It is impossible to get a speed of faster than base Haste speed (i.e. 50% faster than normal) via any means whatsoever. This reduces the benefit of movement speed enhancers; by Chapter 2, once you get Haste, anything else that might boost your movement speed is irrelevant.

Diamond

Although many glitches are fixed on Diamond, it is most notable for its speed stacking rules; there is no longer a speed cap, and there are more ways to boost your speed, so a standard setup would be something along the lines of Monk + Expeditious Retreat + Haste (Expeditious Retreat does not exist in unpatched). In general, there is more content available in the game, but the actual mandatory parts of the game are the same as in unpatched. This means that in Diamond, you move faster and have more options.

Despite many glitches being fixed on Diamond, the two most important (experience/item farming in Chapter 1e and plot item duplication) are still unfixed.