About Texture Streaming, even if my card has 4gb vram I use the 400mb setting otherwise I get bad performance. It loads up lower quality textures initially then upscales them, if you use the lowest setting and zoom with the scope you will notice textures loading after you use the scope and when you exit.
I don't think you need mouse smoothing when aiming because there is this built in effect that the slowest you move your mouse the more resistance there is to movement.