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 is His slave and Messenger.
Removing artificial hair or other ornaments like wristwatch, ring etc., is permissible if they do not prevent water from reaching the skin of the dead person. However, removing them becomes compulsory if they prevent water from reaching the skin of the body. Removing nail polish is mandatory, if it is possible or does not cause any harm to the dead body since it forms a layer on the nails. The reason is that washing a dead body is an obligation and everything that prevents water from reaching the skin should be removed.
Allah knows best.