  Water ice plays a crucial role throughout the different stages of planetary
evolution and is abundant in the Universe. However, its presence and nature in
debris discs of exoplanetary systems are not yet strongly established
observationally. In this study, we quantify and discuss the impact of ice
parameters such as volume fraction ${\mathcal{F}}_{\rm ice}$, blow-out grain
size, size distribution, and its phase on the observational appearance of
debris discs, considering the diverse nature of these systems around stellar
spectral types ranging from A to M. Our findings reveal that the prominent ice
features at approximately 2.7 and 3.3\,$\mu$m depend on both the water ice
fraction ${\mathcal{F}}_{\rm ice}$ and the scattering angle, with
backscattering geometries yielding the most prominent signatures. When the
phase function is considered and data are not background limited, strong
forward and backward scattering (near edge-on discs) are expected to yield the
strongest detections in images/spectra for A or F-type stars, while scattering
angle matters less for later type stars. The Fresnel peak at 3.1\,$\mu$m serves
as a viable discriminant for the transitional phase (crystalline/amorphous),
while simultaneously constraining the water ice temperature. For JWST imaging,
we find that the F356W and F444W filter combination is most effective for
constraining the grain size distribution, while the F356W and F277W filter
combination provides better constraints on the ice fraction ${\mathcal{F}}_{\rm
ice}$ in debris discs. However, degeneracy between the grain size distribution
and ice fraction when using photometric flux ratios means that obtaining robust
constraints will likely require more than two filters, or spectroscopic data.
