I installed the Free version of X8 and it's just a poorly coded Maize Sampler "save as" plugin. Hence the .mse file for the sample content.
There is no way it needs 20+ Mixer strips/outputs for an instrument that's not multi-timbral. He probably exported the instrument in some default multi out configuration.
I've seen this guy Thenatan's stuff before. He seems kind of wonky to me. Better to stick with more competent developers.
EDIT: Ok all you have to do is set the number of mixer strips in Orion to 1, rename the mixer strip from Output 1R to X-8 or whatever then save that as a Template. Then every time you load that template it will have the correct output.
He probably tested it in FL Studio which defaults to a single output and then you can add extra outputs if desired rather than Orion's method of loading them all then allowing you to reduce the unwanted outputs. Reaper asks when you load the plugin whether you want to load the multi outs or a single stereo out.
He might be using a demo version of the Maize Sampler and it defaults to multi-outs or he just doesn't know how to save plugins from within Maize.