Welcome! the M2 uses a faster controller and requires that you use the makerverse software to run it. 15 degrees from vertical is the mounting angle of the main work surface. the M2 isn’t a clone really. it is a second gen version that included the z axis and the newer controller.
WRT your question about beam height, it is to the plane of the motor sprockets. Those are legit questions. There is more about it here if you want to read or link to a video that may be helpful in describing the geometry.