Re: Precisely what energy(ies) are being converted to light in a light bulb?

When a voltage is applied along a conductor, it produces an electric 
field in the conductor that accelerates conduction electrons.  These 
electrons move only a short distance before colliding with atoms within 
the conductor, effectively stopping them.  This process repeats many 
times, resulting in an average "drift velocity" of the conduction 
electrons that is quite slow.
The collisions with the atoms of the conductor causes them to vibrate.
This vibration results in an increase in the internal energy of the 
conductor, which amounts to an increase in its temperature.  When the 
temperature gets high enough, the conductor radiates heat and light.

In terms of your (A) and (B):  The electrical energy (B) gives the 
electrons kinetic energy (A) that is transmitted to the atoms in the 
conductor.  Friction plays no role, unless you want to consider the 
collisions of the electrons with the atoms like friction.  (But, it is 
not friction.)