Performance Tweaking

[Verhängnis]

What is the difference between Full screen 1600x900 and Pseudo 1600x900. Is there any performance gain?
For me Full Screen and Shadows are a must, even if set at a lower resolution and slightly stretched, I will adapt!
Also, is it best to have 2x AA set in-game + 2x AA set through Nvidia Control panel or just leave it with no AA in-game and just the Nvidia settings?

Are there any other config.ini settings I can change to improve performance without much loss in detail?

And finally, does kegety's SFS mod still work and will I be banned from Steam. (Last time I tried it I was banned and had to prove ownership of the game, hella of process that was, damn Steam Employees, dumb as **ck.)
Because I am considering downloading his smaller texture size mod, unless there is another setting in the config.ini.

Thanks for the help.

My specs are:

-Processor: Intel Core 2 Quad Q8200 @ 2.33 GHz
-RAM: 3.5 Gb
-Video Card: GTX550Ti @ 1024Mb GDDR5
-Direct X: 10 (Video card, but Windows XP only supports DX9)