  Constrained Sequential neutrino Dominance of type 2 (referred to as CSD2) is
an attractive building block for flavour Grand Unified Theories (GUTs) because
it predicts a non-zero leptonic mixing angle $\theta_{13}^\text{PMNS}$, a
deviation of $\theta_{23}^\text{PMNS}$ from $\pi /4$, as well as a leptonic
Dirac CP phase $\delta^\text{PMNS}$ which is directly linked to the CP
violation relevant for generating the baryon asymmetry via the leptogenesis
mechanism. When embedded into GUT flavour models, these predictions are
modified in a specific way, depending on which GUT operators are responsible
for generating the entries of fermion Yukawa matrices. In this paper, we
systematically investigate and classify the resulting predictions from
supersymmetric $\mathrm{SU}(5)$ based flavour models by fitting the known
fermion mass and mixing data, in order to provide a roadmap for future model
building. Interestingly, the promising models predict the lepton Dirac CP phase
$\delta^\mathrm{PMNS}$ between $230^\circ$ and $290^\circ$, and the quark CP
phase $\delta^\mathrm{CKM}$ in accordance with a right-angled unitarity
triangle ($\alpha_\mathrm{UT}=90^\circ$). Also, our model setup predicts the
quantities $\theta_{23}^\mathrm{PMNS}$ and $m_d/m_s$ with less uncertainty than
current experimental precision, and allowing with future sensitivity to
discriminate between them.
