Should one recite aloud whike observing both Nafila?

It is optional.You can either recite aloud or silently since it is a superogatory act. I dont think there is an hadith that specifically tells how to recite during nawafils.But,I have heard a hadith that the prophet passed by Umar in the night and heard him reciting loudly during the night prayer. He also passed by Abubakr and couldnt hear his recitation at all.The next day the prophet asked why each recited the way he did.Umar replied that he recited aloud to keep shaytan away and Abubakr said he didnt want to disturb people who were sleeping. The prophet advised Umar to reduce his voice and Abubakr to raise his voice a little. So, with my little understanding ,I think u can do any of the two whch is convinient for you. And Allah knows Best.