Hi seandavid, welcome to the forums. I'm a newbie myself and the Double Eagle is my first Omega. I'm only a WIS in training but I can get the ball rolling with some general info while the real WIS provide the nitty gritty.
The Constellation prior to the Constellation Double Eagle was available in quartz (1532), mechanical (1120) and perpetual calendar (?). The Double Eagle was offered in Perpetual Calendar (1680 thermocompensated) and the newer mechanical Co-Axial Escapement (2500) only.
I'll have to abstain from the Chronographs, maybe someone can jump in and fill in the blanks there.
The Double Eagle was also offered in a larger mens size option of 39mm and midsize 35mm, as opposed to the largest size of the prior Constellation mens size of 35mm.
The last redesign of the Constellation line prior to the Double Eagle was with the Manhattan model many years back. Otherwise it has remained largely unchanged. Until now.
The new design Double Eagle is a love it or hate it choice among Omega followers, particularly Constellation fans. The most flattering comment I've read regarding the Double Eagle design is that it shares a similar controversy to the PloProf. You wouldn't have bought one because you thought it was ugly when it was new. And this may be precisely why these models turn out to be the classic must haves a few decades later due to their commercially low profile during their time.