  Cluster number counts will be a key cosmological probe in the next decade
thanks to the Euclid satellite mission. For this purpose, cluster detection
algorithm performance, which are sensitive to the spatial distribution of the
cluster galaxy members and their luminosity function, need to be accurately
characterized. Using The Three Hundred hydrodynamical and dark matter only
simulations we study a complete sample of massive clusters beyond 7 (5)
$\times$ 10$^{14}$ M$_{\odot}$ at redshift 0 (1) on a $(1.48 \ \mathrm{Gpc})^3$
volume. We find that the mass resolution of the current hydrodynamical
simulations (1.5 $\times$ 10$^9$ M$_{\odot}$) is not enough to characterize the
luminosity function of the sample in the perspective of Euclid data.
Nevertheless, these simulations are still useful to characterize the spatial
distribution of the cluster substructures assuming a common relative mass
threshold for the different flavours and resolutions. By comparing with the
dark matter only version of these simulations, we demonstrate that baryonic
physics preserves significantly low mass subhalos (galaxies) as have also been
observed in previous studies with less statistics. Furthermore, by comparing
the hydro simulations with higher resolution dark matter only simulations of
the same objects and taking the same limit in subhalo mass we find
significantly more cuspy galaxy density profiles towards the center of the
clusters, where the low mass substructures would tend to concentrate. We
conclude that using dark matter only simulation may lead to some biases on the
spatial distribution and density of galaxy cluster members. Based on the
preliminary analysis of few high resolution hydro simulations we conclude that
a mass resolution of 1.8 $\times$ 10$^8$ h$^{-1}$ M$_{\odot}$ will be needed
for The Three Hundred simulations to approach the expected magnitude limits for
the Euclid survey.
