Am I wrong, or is that 32x24 area actually cut through with narrow walkable areas? The Mount Galardrym area feels like you're on roads through the area, and you cannot leave them. So (unless I'm mistaken, which is a distinct possibility), it might say 32x24 on the area size, but that doesn't equate to that much open, walkable area. Right?
You can have a 32x32 open area, I put one of that size (it was fairly flat farmland) in one of my campaigns. Performance at that size can be an issue, moreso for PWs than single player. That area size is large enough the builder needs to take care to give the player something of interest so they dont just get bored walking through it.
With the ability to scale things in nwn2, including the players, people have made areas that seem even larger than the 32x32 limit by scaling everything down, allowing for pseudo 64x64 or96x96 areas.
Nwn2 does have a hardcap on the number of objects that can be in an area. Its around 3250, and depending on how detailed you make things you can get to that limit in a smaller area, particularly if you use something like the building construction kit (bck) someone made, the bck is basically small sections of walls/floors/roofs that you can use to make custom buildings from.