Biggest difference for Drengin is their factories have a military adjacency bonus in addition to the manufacturing ones. The line that leads to Planetary Invasion is also a bit different, with an awesome colony unique building that gives Military Manufacturing (this is a separate multiplier from regular manufacturing, that acts only on the % the planet sends to military as opposed to social). They've also got some different names for techs that are more brutal sounding but looked about the same to me.
But yes, lack of a Civilopedia equivalent in-game really hurts, gotten so used to it in Civ5, Civ:BE, and AoW3.
