Distributions of the main structural parameters in the data sets used in this work, along with the redshift and the stellar mass used for our forecasts. We also show the bulge to disk flux fraction (bulge fraction) for the Flagship. The y axis is the normalised density counts such that the area over the curve is equal to one. For the magnitude, the COSMOS histogram shows the F814W magnitude and the Flagship one corresponds to the Euclid VIS magnitude. The range of the training set (COSMOS) covers most of the Euclid data.