--will not affect balance per se, as that is controlled by larger fibers. All motor neurons are also larger, myelinated ones, so muscle weakness is not generally associated with it either.

That having been said, though, many people have mixed types, in which both small and large fibers have some damage. Also, as dahlek points out, if you have small-fiber symptoms of pain and numbness, moving is going to become more difficult (you may not feel up to doing it as much) and lack of exercise may result in muscle weakness and balance difficulty (especially if there's numbness). It's part of the reason why most of us would say one with small-fiber neuropathy (indeed, any neuropathy) should exercise to the limits of his/her tolerance--lack of physical activity only tends to make things worse.

Sophisticated neurological testing (EMG/NCV, manual mucle testing) should be able to distinguish between muscle deterioration that is caused by de-enervation and that which is caused by lack of exercise. People who are bed-ridden or otherwise incapacitated are hard to tell from people with de-enervation without such testing. Balance is a bit easier to test--but people with balance problems may have cerebellular, sinus, or semicircular canal issues that have little to do with neuropathy.