The wood is I don't know, probably fir or pine or hemlock, but it's rated for ground contact, Copper Azole pressure treated.
The superstructure is just regular premium 2x4 material, picking the straightest each time I went shopping.
As for digging and posts and footers.. good question.
The short answer is I could only have the top of the deck about 3-6 inches above the height of the concrete. Otherwise I'd have to step down from the deck to get into the house. I didn't have room to build a deck that "thick".
Here's the post with a longer explanation and a picture for reference.