MicroQuilter is a Superior Threads brand name, so if your cone says MicroQuilter, it is from them.
I don't see why you can't use the 100 wt thread to quilt with. A heavier weight thread will show up more, while a fine thread won't. If you're just practicing, you might want to use something heavier so it's easier for you to see and learn from. Finer threads are also good for quilts where you want the piecing to be the focal point, not the quilting.