It’s funny you say that. I’m on the FluidNC discord and went down that route with one of their devs.
To answer your question, yes you can change the stepper pulse to look for the rising or falling edge by appending :low or :high(default) to the step pin in the configuration. When I tried that, the problem seemed to worsen. Here is the link to the Ruida issue that you speak of. It does feel very much like that issue, and at one point I was convinced. Oz did a good job explaining the issue and how to fix it.
I do have my stepping engine setup as I2S_STATIC which is recommended for lasers. I originally had it as I2S_STREAM and the output was very wonky. That was the first issue I had with my configuration file.