This drama is not a spin-off of 10 Miles of Peach Blossom. It's indeed produced by the same team (director, costume designer..etc.,) but comes with a completely individual story. The background story is similar to Peach Blossom - both r based on Chinese mythology. Apart from this, there's not much to compare.
The story focuses strongly on Chinese moral principles - courage, justice, faith and love. Faith is a better way to describe the main storyline. There were certain times that the protagonists had to make decisions within time was given and they really did their best as they had faith in each other. This is the part attracts me the most - romance needs to be built on something reasonable and faithful. Something we (as the audience) can rely on. So it's not just a simple romance drama. We get to know the roles well like our dear friends. Thanks to the excellent acting from Chang Chen and Ni ni, the chemistry is genuinely emitting in all the later episodes (possibly the first 6 ep were being slow as the story was in need of time to build up the background-part).
It is a good drama. Enjoy it.