Hi i'm a complete noob about forums and modding, so be patient if i'm doing something wrong. Anyway about your problem with the dress position in relation to the body, I don't know why that happens but you can move the dress, i think there is an option in the shape tab, click on the dress (in your right side of the screen), click on the shape tab (top left of the screen) then select the option , i think it's called move shape. then a box appears and you input the coordinates. It's less complicated then it appears.

Vanilla meshes are kinda funny that way. If you open nifskope and look at the XYZ values of a NiTriShape, you'll see that they have arbitrary number values, resulting in the misaligned mess you have.

Thankfully this a stoopid (lol) easy fix. Just enter the same xyz values back into Outfit Studio's "Move Shape" feature under the "Shape" tab and PRESTO! Misalignment be gone.

Cell said something similar: http://www.loverslab.com/topic/25180-unofficial-bodyslide-2outfit-studio-tutorials/?p=1076244

And that helps a lot... but not quite enough. I want to be writing another blog post about this...