To summarize all –
There are basically two shitos and two issues:
A – Halachak Talmudic – d’Oraisa based – Das Moshe:
1) The שלטי הגיבורים, Rema, Magen Avrohom – that permit wearing Pe’ah Nuchris – even if its your OWN NATURAL hair and in Reshus haRabim.
2) Be’er Sheva, Yavetz etc – that uphold ALL Sheitlach that resemble anything to hair are Assur in Reshus haRabim.
(Note, there is no ‘inbetween’ halacha of “wiggy” looking coverings)
B – Minhag of Das Yehudis –
Relatively based – depends on the towns custom minhag, on what is defined as modest at the time.
1) The Minhag in most cities and towns in Europe and many Mid-East countries – until 150 years ago (give or take) – women covered their hair with a Maftachos.
2) The accepted minhag as of today – most Charedi women don a Pe’ah Nuchris.