How can I create seperate low- detail models for my mod?
You create art that is the same as the normal art but low-detail. The objects (meshes, skeletons, bones, animations etc) have the same name as the normal art. The only difference is that you append _l to the end of the filename. So if the normal art is test.w3x, the low-detail art is test_l.w3x. The SDK will then take care of the rest and compile your low-detail art correctly.