Is the duration of atomic/electron phenomena proportional to the wavelength of photons produced by those phenomena? Given that any periodic electromagnetic emission has a wavelength due to its time related oscillation and a finite speed of propagation, is it the same for atomic/electron phenomena, such as the emission of photon by an electron jumping to a different level of energy and/or desintegration of pairs of particles?
i.e. is it assumed those process are instantaneous or slower? And if they are not instantaneous, how can they still be quantized? I mean, I would suppose a non-instantaneous process can be interrupted.
Does the quantization of energy imply an infinitesimal delay or an infinite speed of »manufacturing» for photon generation?
 A: 
Is the duration of atomic/electron phenomena proportional to the wavelength of photons produced by those phenomena?

The wavelength of the photon is inversly proportional to its energy, E=hν=hc/λ , the functional relation is not proportionality but depends on the quantum mechanical solutions of the particular phenomenon.
You ask:

Given that any periodic electromagnetic emission has a wavelength due to its time related oscillation and a finite speed of propagation, is it the same for atomic/electron phenomena, such as the emission of photon by an electron jumping to a different level of energy

The photon is not an electromagnetic wave, it is an elementary particle with zero mass and the way it interacts with an atom depends on the quantum mechanical solutions for the particular atom. The orbitals of the electrons about the atom have different energy levels and thus different energy photons can interact with the atom, and the energy line has a width, which determines the time constants for the interaction, different for different atoms and energy levels, see for hydrogen as anexample.

and/or desintegration of pairs of particles?

In general the particle lifetimes  are associated through the uncertainty principle with the width of the interaction. These are different for different interactions,  ( strong, weak , electromagnetic) scatterings or decays, depending on the particle charachteristics.
