Euclid will collect an enormous amount of data during the mission's
lifetime, observing billions of galaxies in the extragalactic sky. Along
with traditional template-fitting methods, numerous machine learning
algorithms have been presented for computing their photometric redshifts
and physical parameters (PPs), requiring significantly less computing
effort while producing equivalent performance measures. However, their
performance is limited by the quality and amount of input information,
to the point where the recovery of some well-established physical
relationships between parameters might not be guaranteed. To forecast
the reliability of Euclid photo-$z$s and PPs calculations, we produced
two mock catalogs simulating Euclid photometry. We simulated the Euclid
Wide Survey (EWS) and Euclid Deep Fields (EDF). We tested the
performance of a template-fitting algorithm (Phosphoros) and four ML
methods in recovering photo-$z$s, PPs (stellar masses and star formation
rates), and the SFMS. To mimic the Euclid processing as closely as
possible, the models were trained with Phosphoros-recovered labels. For
the EWS, we found that the best results are achieved with a mixed labels
approach, training the models with wide survey features and labels from
the Phosphoros results on deeper photometry, that is, with the best
possible set of labels for a given photometry. This imposes a prior,
helping the models to better discern cases in degenerate regions of
feature space, that is, when galaxies have similar magnitudes and colors
but different redshifts and PPs, with performance metrics even better
than those found with Phosphoros. We found no more than 3% performance
degradation using a COSMOS-like reference sample or removing u band
data, which will not be available until after data release DR1. The best
results are obtained for the EDF, with appropriate recovery of
photo-$z$, PPs, and the SFMS.