Definitely better than Kenki Koiuta. I can't say it expands on the world that much more than than spin-off, but it does it in a much better way, while also expanding on Emilia and Puck characters, and their history. It also has way better pacing, makes more sense structurally and is generally more interesting, since it's not just "I am the edge of my sword, I hate everyone just because, and do not want to admit I have any other feelings" type of story during a generic racism-based war. Although, this manga also touches on racism, obviously, since it is part of Emilia's character.
If you are a fan of Re:Zero - definitely can recommend. And if you do not want to read the manga, there is also anime adaptation, and from what I remember it was just a tiny bit more fleshed out in little things.
