So, what it is then? Just as first season's specials, those are short stories focused around R2 story, with some telling about things from past and last episode happening after R2 epilogue. The reason why I'm saying to ignore genres is how meaningful this special is. While there is some fanservice, all episode add to the main story and are on the serious side. Some also hit in the feels.
Just as the title says, it's a picture drama. In other words still frames with voice (and subs) telling story. It's worth mentioning that art is far better than in previous picture drama - here all episodes use same drawing style and move "panels" through screen for better effects. It looks less like random collection of leftover frames put together into something and more like actual work of art.
Personally I really liked the way it looked and didn't have any problems with it not being full animation.
Characters and music are from main series, so there is no reason to comment on that.
I really recommend watching it to anyone who enjoyed both seasons of Code Geass. Even if you generally don't like picture dramas, I encourage you to give it a try - it's worth it.
