I only watched them twice. When I watched them, they played a 4-2-3-1/4-3-3 of sorts. The basic idea is a striker, an attacking midfielder behind him, and then two attacking wingers, that you could consider forwards because of high up the pitch they play(hence 4-3-3), and two central midfielders. The central midfielders seem to be decided already, they're going to play with Modric and Kroos. The wingers, AM and striker are the positions they've shuffled around with from what I've seen. They played Bale as the attacking midfielder in some games, while in others he played on the right. Isco/James played on the right whenever Bale was played in the AM role. Ronaldo almost always played on the left and Benzema as the striker. Jese was also played as the striker in some games, and in others on the wings.
In a nutshell, I'd say the 4 attacking positions will be interesting, while the 2 CM's and the defense are pretty straightforward.