I think the 'Boxers' book was easier for me to envision as a comic, because they were on this epic journey. These teenagers basically gathered into this army and marched to the capital city where they had a showdown with the Europeans and Japanese. On the 'Saints' side, it was a lot trickier.
In my research, I learned that the Boxers' kung fu wasn't all that formalized. The vast majority of them didn't belong to some age-old martial arts tradition. They were basically poor, starving teenagers doing the best they could to figure out how to fight, relying more on their mystical beliefs than formal training.
I wanted to make an explicitly educational comic that taught readers the concepts I covered in my introductory programming class. That's what 'Secret Coders' is. It's both a fun story about a group of tweens who discover a secret coding school, and an explanation of some foundational ideas in computer science.