Is it permissible to vocalize during the supererogatory Maghrib or Fajr prayer if a man prays with his wife, or are the supererogatory Fajr, Maghrib, and Isha prayers not to be vocalized?

A worshipper may lower their voice during supererogatory prayers in the daytime. As for night prayers, one has the choice between vocalizing (Jahr) and lowering the voice (Israr), though vocalizing is better. This is because both manners have been authentically reported from the Prophet, peace and blessings be upon him, who at times lowered his voice and at other times raised it. This is the opinion of the majority of jurists. As for the regular supererogatory prayers (Sunan Rawatib) accompanying the obligatory prayers, all of them should be performed silently. There is no harm in performing the regular supererogatory prayers of Fajr, Maghrib, and Isha either silently or audibly.