I have an xps13 with Debian.
1) The developer edition, as far as I can tell, has not been updated to 8th gen intel CPUs which offer a quad core U-series. It might be a better bet to just get the most updated XPS and install Linux on it.
2) There have been some images shared by dell that suggest a redesign of the XPS line is imminent, possibly at CES in a week or so. It might be wise to wait a little to see if there are some nice updates on the horizon or good deals coming on existing models.