I use Dropbox XL/NC to edit on multiple computers. Of course, Dropbox syncs everything but if you wanted to just copy the essentials on a thumb drive, you would need your sequence xmls, all the xlight_* xmls, plus your songs. In addition, you'll need any images and videos your sequences use.
One caveat with using Dropbox on multiple computers: XL/NC uses an absolute path to images, videos, and maybe other stuff. If your user path is different on your machines, XL/NC won't find them. For example, my home machine has C:\Users\PL\Documents\My Dropbox\House\Christmas Lights\xlights v4 as its path, and laptop has C:\Users\plaberge\Documents\My Dropbox\House\Christmas Lights\xlights v4. I still edit files with images on my laptop but typically don't touch the parts of the sequence that refer to images. If I really need to changes these, I edit the xml files with Notepad++ to change the paths from one to the other.