For by far most users the only thing they need to change is the VideoMemorySize and ReservedMemorysize.
Autodetect will always put in your VRAM amount since that is what you should use as a baseline value. Is it the best and most optimal value? Perhaps not since it depends on how much total memory you have to throw at the game.
If you have 12Gb+ RAM you can use values for videomemorysize up to 8Gb. if you got more you can increase it further but not much point since it is almost impossible to get skyrim to use much more without starting to getting massive slowdowns due to bandwidth issues anyways.
The reservedmemorysize is either 256 or 512 for just about all computers. If one does not work try the other.
As for all the rest.. unless you start getting performance drops during panning the camera or during transitions you do not need to worry about changing them from the nexus default value for your card.
In general the values suggested to you are a very good starting point. As you add more stuff to your game and you start getting into CTD and slowdown issues you can return and try to change the values.
Hope that helps otherwise just ask which parts you want clarified.
Thanks... I wasn't really asking for myself though, more pointing out an inconsistency in the guide (the whole "don't use nexus version" followed by "pick the one corresponding to your graphics card" (which is only in the nexus version))... I feel pretty comfortable configuring this myself, but that might cause major confusion to newer users.