NWN does render every face... that is why backface culling is turned ON not OFF. This is a feature of whatever 3d editing software you use. 3dsmax has a global option to either turn ON backface cull or to turn that feature OFF. The total number of polys is directly related to whether or not you cull those back faces or not. NWN will attempt to render and backface poly IF it exists, even when you will never see it. So, it is typically best to leave back face cull turned ON so that the back faces are NOT created, except in the few instances, like plants, where you might wish to have something visible from the other side.
The feature in Veltools is a very powerful feature, and one of the many reasons I recommend using Veltools along side NWmax, so that you have the power to use those extras. Warning that Veltools doesn't work all that well in later versions of 3dsmax, past version 10. I have been attempting to fix the features that don't work in the later versions but it proving problematic. If you have 3dsmax 5-10 veltools will work fine, so will nwmax and velmar's tileset creator, past version 10, multiple features of all of them have issues, some much more problematic than others. NWMax has been the easiest of the three to get working, but when I fix it to work with the later versions, it no longer works in Gmax correctly, so again, it is proving problematic.
3dsmax version 9 is almost worthless as it doesn't properly save or read what is saved as options... as in adding search folders for paths for textures etc, version 9 does not seem to save those options, even though they are listed in the proper places as optional search paths, when you open a max scene file, version 9 tends to re-adjust the settings according to whatever the scene originally had, even when you change it and re-save the scene... meaning, it never overwrites the actual extra folder locations back into the scene, so, you have to add those folders back to the search path every time you open an older max scene file. Real, royal, pain in the arse. Version 10 seemed to handle those options better, but I no longer have a working version of 10 or 11 or 12 or 13, all I have now is 9, and 14 and 15. I can't get gmax to install on windows 8.1 no matter how I set it up, the setup fails every time. Even when setting the options to use compatibility mode, it doesn't work. So, I am having to have someone else test the scripts when I make a change, and so far, I can't seem to get the features to work past version 10.
So, anyway, as direct answer to the op question, yes there is an option to automatically turn backface cull OFF, but it is certainly NOT recommended for NWN due to the limits the engine has with calculating the number of faces that are truly visible to whatever position the camera is located, meaning that the engine must recalculate every single face that may be visible, then calculate whether or not that face casts a shadow, so the reduction of faces is the primary goal. Yes, we, the community in general, has proven that the engine can handle a bit larger number of total faces, but the engine and general game play benefits from having as few total faces as possible on any given object and most particularly in any given 10meter by 10 meter square, which is then added to the total number of faces in the other 8 10x10 squares in any give 3x3 group, where the camera/pc is located in the central square with an extra square visible in every direction from that center. so, 9 10x10 squares are what the engine calculates against, and what causes the general FPS speed all the way through.
My issue has always been that by default, 3dsmax has backfaces turned ON, meaning backface cull is turned OFF by default settings in 3dsmax. Then I have to check against whatever settings any general creator has chosen to implement, I find that I have to wade through each tile and REMOVE back faces a lot of times, to reduce the wasted calculation times, and lost speed. In general, you are better off with back faces removed except in the few instances where they are actually needed, as in foliage that can be viewed from both directions.
