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Cosmic rays (CRs) are dynamically important for the formation and evolutionof galaxies by regulating star formation and by powering galactic outflows.However, to what extent CRs regulate galaxy formation depends on the couplingstrength of CRs with the ambient plasma and the effective CR transport speedalong the magnetic field. Moreover, both properties sensitively depend on theCR momentum, which is largely unexplored in three-dimensional hydrodynamicalsimulations. We perform magneto-hydrodynamical simulations of entire galaxieswith masses ranging from $10^{10}$ to $10^{12}\,\mathrm{M}_\odot$ and comparedynamically coupled CRs in the grey approximation with a spectrally resolvedmodel that includes CR momenta from $0.1\,\mathrm{GeV}~c^{-1}$ to$100\,\mathrm{TeV}~c^{-1}$. We find that hadronic cooling of CRs dominates overAlfv\'{e}n cooling, with the latter emulating CR losses as a result ofstreaming of CRs down their pressure gradient. While star formation rates andgalaxy morphologies are only mildly affected by the spectral CR modelling, massloading factors of galactic outflows can differ by up to a factor of four indwarf galaxies. All simulated low-mass halos ($M=10^{10}$, $10^{11}$, and$3\times10^{11}\,\mathrm{M}_\odot$) drive strong outflows, where CR transportis temporally dominated by advection. In contrast, the Milky Way-mass galaxywith $M=10^{12}\,\mathrm{M}_\odot$ does not drive sustained outflows, so thatCR transport is entirely dominated by diffusion. The effective energy weighteddiffusion coefficients vary by two orders of magnitude from the canonicalenergy-weighted values of$\langle{D}\rangle_{e_\mathrm{cr}}\sim10^{28}\,\mathrm{cm^2\,s^{-1}}$ in thedisc up to $3\times10^{29}\,\mathrm{cm^2\,s^{-1}}$ in the circumgalacticmedium, where we observe substantial temperature and CR pressure differencesbetween our grey and spectral CR models.

Spectrally resolved cosmic rays -- III. Dynamical impact and properties of the circumgalactic medium