One of the nice thing about layers is that you can lock an image down to the screen or make it invisible. Invisible is good if you are working on an espescially complex drawing.

Xara Xtreme's Layers work a little differently than what I'm used to, but they are similar to most programs. The attributes and etc. you assign on one layer should not affect the others, especially if that layer is locked down (unchecked.)

You can also export that layer and work on it separately if you need to do so. I would use caution on exporting complicated fills or transparencies though. But, basic line art is fine.