Are there different ways to create photons? I don't think a previous question How are photons created? answers my question, which is.
As far as I know there are at least three ways to create photons:

*

*Electrons jumping between levels in an atom.

*Charged particles accelerating, even a proton by itself in intergalactic space with no electron in sight.

*Matter-antimatter annihilation, including proton-antiproton annihilation again with no electron in sight.

Is there a unified explanation for these three seemingly distinct cases?
Secondly, is there evidence that photons are quantized in all three cases?  From what I read, Planck's quantization hypothesis was based on black body radiation, which only applies to scenario 1 above.
Thanks.
P.S.  One main reason for my question is the role of protons and oher particles.  QED and most of the literature only talks about electrons.
 A: A quantum of a quantity means that it comes in  countable steps. It does not mean that the value given is not continuous. A number of bricks describes how many there are. It does not mean that the weight of a brick cannot be any number  within the continuum of weight.

Is there a unified explanation for these three seemingly distinct cases?

All can be modeled by quantum field theory, and at the limit of h_bar compatible with zero (macroscopic), Maxwell's equations.

Secondly, is there evidence that photons are quantized in all three cases?

Photons are countable in all three cases, their   their energy is $hν$    where  $ν$ is the frequency of the electromagnetic wave they will belong to when in large numbers.
In transitions between bound states they have they come in quanta defined by the energy differences between states.
Particle interactions as annihilations and decays, are modeled by the QFT of  standard model.
In two body annihilation to two photons just the kinematics and conservation laws are enough to define the energy of the photons.
