All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
It is understood from the question that these cloth fibers are mere threads, so they do not prevent water from reaching the skin or hair underneath them because they are not stuck to the skin or hair. Hence, you do not have to remove these fibers before performing ablution. As for their presence after ablution, it definitely does not harm.
Allah knows best.