NWN and NWN2 save files are ridiuclously freaking huge because it contains the ENTIRE module file in each save (with modifications to the module file to account for changes you made to different areas).
On the plus side this means old saves will work.
On the down side it means updates and bugfixes will NOT apply unless you start a new game. (although some might be added at module change on a multi module campaign like the official campaign).
And also on the down side the saves files ridiculously huge.
Characters are their own file saved individually in a characters directory that would work with any module and updates combination. So expect no issues with exporting/importing characters (unless missing a hak which only comes into play if you hypothetically exported a character from an installation with the expansions which had expansion specific items, then uninstalled the game, installed only the base NWN2 without installing expansions, and then tried to import that character.)
touched: The saved games and any characters you may have exported are located in your Documents folder, in a Neverwinter Nights 2 folder.
A note to the wise, to avoid incompatibilities and a whole freaking mess keep a different unique copy of that folder for each custom module (which are installed into said folder).
That is, if you want to install a custom module called "A haunt through the dark" then rename the existing folder with the addition of "- official campaign" at the end. then run the game and it will create a new blank folder in documents.
Then install the custom module into that folder and run it.
When you want to install a different custom module, repeat the process. you will get a whole bunch of folders over time but it will save you a whole bunch of headaches.
