RV Tauri stars have pairs of maximums and minimums on phase curve due to them variability. Are there other types of pulsators with the same "double" cycle, with phase curve shape similar to EW?
The main objects that show double-modes are delta Scuti stars or SX Phe stars. Over the years there have been many stars mislabeled in the SIMBAD database, either a delta Scuti is really a W UMa, or a W UMa that is really a delta Scuti. In reality the curves often look more like mirror images of each other, but the light curve changes can be subtle. In delta Scuti stars you don't have the double phase, you see more a beat envelope that is caused by the the difference in the two active pulsations.
In distinguishing Galactic delta Scuti pulsators from eclipsers and other types of variables, the Ogle group (Soszynski et al. 2021, Acta Astronomica 71, 189) noted several criteria that they found helpful. These involved looking at light curve morphology and period ratios.