${\mathrm{EuFe}}_{2}{({\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x})}_{2}$ hosts complex dynamical processes resulting from the interplay of its two electronic ground states, i.e., ferromagnetism and superconductivity. A detailed understanding of the observed dynamics is, however, still missing. In this sense, frequency-resolved experimental techniques can be crucial to disentangle the magnetic and/or superconducting origin of the phenomenology and to contribute to its modeling. Here, we report on the investigation of ${\mathrm{EuFe}}_{2}{({\mathrm{As}}_{0.7}{\mathrm{P}}_{0.3})}_{2}$ based on muon-spin spectroscopy and ac magnetic susceptibility ($\ensuremath{\chi}$) measurements. The dependence of the internal field at the muon site on temperature is indicative of ferromagnetic ordering for the ${\mathrm{Eu}}^{2+}$ magnetic moments and only the conventional magnon scattering governs the longitudinal relaxation rate at low temperatures. At the same time, we observe a rich phenomenology for the imaginary component of the susceptibility ${\ensuremath{\chi}}^{\ensuremath{''}}$ by means of both standard ac susceptibility and a technique based on a microwave coplanar waveguide resonator. In particular, we detect activated trends for several features in ${\ensuremath{\chi}}^{\ensuremath{''}}$ over frequencies spanning ten orders of magnitude. To explain our results, we propose a model for the complex dynamics of vortices and antivortices influenced by the underlying structure of magnetic Meissner domains based on the identification of intra and interdomain depinning processes.