if you watch a lot of these women doing their wigs on Youtube, they spend ALOT of time using tweezers to thin the hairline out by plucking it to look a lot more realistic, so its not a wall of hair. Women of colour dont tend to have a full harsh hairline like other due to braiding ( i guess) so this look suits them and looks incredible. i am not sure if it would work for a man wearing a hair system ..
If you look on Youtube, you can see alot of women who wear wigs , bleaching the hairline and they even show you how they achieve it. Its not hard, and it has some amazing results ..... bear in mind that a lot of the "melting" into the scalp is also make up , which most men do not end to use to conceal the hairline