Is it better to separate every two Rak'ahs in the Sunnah and voluntary prayers, or to combine them in daytime prayers and separate them in nighttime prayers? And what is established in the Sunnah regarding that?

The best way to perform supererogatory prayers (Nawafil) during the day and night is two rak'ahs at a time, based on the Prophet's (peace be upon him) saying: "The prayer of the night and day is two by two." And 'Aisha (may Allah be pleased with her) said: "The Prophet (peace be upon him) used to pray eleven rak'ahs between finishing the 'Isha prayer and Fajr, performing the taslim after every two rak'ahs." As for her statement: "He would pray four (rak'ahs) and do not ask about their beauty and length, then he would pray four (rak'ahs)," her intention was that he would pray four but perform the taslim after every two rak'ahs. What has been authentically reported about him (peace be upon him) regarding his praying three, five, or seven (rak'ahs) at night is understood to refer to the Witr prayer.