Is it better to pray supererogatory prayers at home than in the Prophet's Mosque, given that they are multiplied by more than a thousand prayers in Medina, and does this apply to all types of supererogatory prayers?

Voluntary (nafila) prayers performed at home are better than those performed in the Prophet's Mosque, and the extent of this superiority is known only to Allah. Some scholars are of the opinion that the multiplication of prayer in the Prophet's Mosque by a thousand prayers applies specifically to obligatory (fard) prayers, not voluntary ones, because performing voluntary prayers at home is closer to sincerity. Sheikh Ibn Uthaymeen preferred this view and included the optional prayers performed in the mosque, such as the Ramadan night prayers (Qiyam Ramadan) and the prayer of greeting the mosque (Tahiyat al-Masjid).

The Shafi'is hold that voluntary prayers in the Prophet's Mosque are multiplied, but performing them at home is still better. Abundance of reward does not necessarily imply superiority. Some scholars have gone further, stating that voluntary prayers performed in homes in Mecca and Medina are better than performing them in the two Mosques. This does not contradict the fact that voluntary prayers in the two Mosques are better than elsewhere, with the exception of homes in Mecca and Medina.

In summary, performing voluntary prayers at home is better, but if one performs them in the Mosque, they will still receive the aforementioned multiplication.