All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is permissible for you to pray the four Rak'ahs of Rawaatib (confirmed or unconfirmed supererogatory prayers connected to obligatory prayers) in twos with two salaams, and it is permissible to pray them with two Tashahhud but with one salaam. You are not obliged to say salaam (to finish the prayer) at the end of two rak'ahs.
However, the scholars differed about which way is better.
Imam Malik, Ahmed and Ash-Shafi'i are of the view that it is better to say salaam (finish the prayer) after every two Rak'ahs, as the prophet said: "The prayer (voluntary prayer) of the night and day is in twos." [Ahmed and others]. Nevertheless, Abu Haneefah is of the view that it is better to pray the 4 Rak'ahs with one Salaam. He provided the evidence of what Ibn 'Umar used to do, as he used to pray the voluntary prayers during the day in 4 Rak'ahs, (with one Salaam).
The matter in this regard is easy, it is permissible for you to pray the Rawaatib prayers in twos with two salaams, or in 4 Rak'ahs with one salaam and two Tashahhud.
Allaah Knows best.