Lightroom :: Moving Versus Copying Image Files To External Disk

I'm going to move my image library, catalog and ACR cache to an external drive so that I can work with a consistent set of files and edits on multiple computers. I know what I need to do to move the catalog, and I know how to move the image files to the new drive so that LR is aware of the move.
 
But what I'd really like to do is copy the image files to the new drive while leaving the existing images on the internal drive as a backup. As far as I can tell, LR doesn't support copying of images within the program. If I copy the files outside of LR, without deleting the originals, LR is going to conitinue to point to the orignal files on the internal disk.
 
So, if I right click on a folder in the Library module folder tree, there's an option to Update Folder Location, and this seems to do what I need it to do, although I've only tried it on a single folder. Will Update Folder Location work to relink an entire folder tree in one operation?
 
One related question:  Where does LR store it's preferences? One of the catalog specific preferences is Standard Preview Size.  My desktop has much higher res monitors than my laptop, so if this setting is stored in the catalog then I'll have to pick one value for both computers. I'm thinking it would be better to use the larger value, for the desktop, but I'm not sure how that will play on the laptop. (It would be nice if this were computer specific, rather than catalog specific.)