Lots of questions on the various inhabitants of the BM universe and whether they are bio-mechanical or not. I held off answering until I could consult with the story team, but now have an answer for you.
As you know, MU characters are bio-mechanical. A Toa or Matoran or Dark Hunter, etc. is normally about 85% mechanical and 15% organic (the organic being muscle tissue, lungs, etc.)
BM characters are also bio-mechanical -- however, they are more like 85% organic and 15% mechanical (note that helmets and armor do not count as part of the mechanical, since they are just equipment that can be put on or taken off. I am talking actual permanent mechanical parts of the body.)
So BM beings are closer to, for example, an organic being who happens to have some mechanical implants, as opposed to a largely mechanical being who happens to have some organic elements.