Screenshots do not do this game justice. I saw it way back at E3 and it looked downright amazing, which is remarkable considering it was obviously a pre-alpha build. The very low system requirements just allows the game to scale a lot more for more people to enjoy it, but if you set this thing to max, I'm sure you'll be blown away. During the roundtable discussion, the man even said that the PC will have the best graphical performance because they want to optimize it for the different platforms rather than setting some common bar among all three.
Exploration is done either by boat (which you have a navigator/helmsman to handle it for you) or by foot, where you get to have a crewman with you to assist. There will be a lot of different environments and towns to visit in this regard.
Have not heard about the LE but it is a pretty safe bet that it will since they're looking to make Risen 2 a success.
As far as DRM for the first game is concerned, I know they said a couple of weeks ago they were removing the TAGES garbage from the Steam version, and you would be able to download a DRM-free version which should be going live real soon. By the way, you DO NOT need to have played the original to play this one because the story is a separate one.
If you have any other questions I will try my best to answer them through my experiences I had.