HFMDE and LFMDE are cherry product codes. Doubleshots are a type of keycap, made by a process called injection molding, you can read about it more in the getting started wiki here on GH.
The g80-3000 are full size, the g80-1800 is actually a more compact layout, which still retains the numpad, albeit in a smart way to save space.
here is a pic showing a 3000 and an 1800 side by side:

a quick note...the 1800 theoretically has blacks, but I could switch the switches for blues from my numerous g80 donor boards.