If Phenibut/Kavinace are CCB's and they are marketed as GABA...
They aren't actually marketed as GABA; they're marketed as GABAergic drugs, which means that they stimulate the production of GABA.
it makes me unclear which other forms of GABA might also be CCB's?
There's only one form of GABA, and it's not a calcium channel blocker. But as noted, it doesn't cross the BBB, so supplemental GABA will not work unless you have a leaky BBB (which many of us do).
There are various different GABAergic drugs with various side effects; benzos are also relevant here because although they don't create GABA, they increase the effects of GABA. But tolerance is a problem with all of these drugs, though the extent of the problem varies by drug. Also, many of these drugs can be extremely addicting, and must be taken with great care.