North Africa is most likely to be largely Berber (at the exception of Egypt), with diverse degree of Romanisation, with the Mauri/Africani/Romani divisions probably going to lives on.
Basically : from less to more importantly romanised Berbers, distinguished from coastal Romance populations.
Now, Byzantine Africa (strictly speaking) went trough an important cultural and political decline : it seems that Constantinople more or less cease to really care about the province in the late VIth century, more or less as remote lands of the Empire (in spite of its known prosperity).
Any Greek presence, ethnically speaking, would be fantasmagorical.
Maghreb is most likely to stay out of most post-classical Romanity, except some tiny isolated as Volubilis. While a Gothic influence is possible, without being likely (at the contrary, giving the difficulties Spain was undergoing : Gothic kings never really managed to go outside the peninsula, eventually) and to say nothing of a forseeable conquest.
It's more likely to see a really tiny Romance presence on Mediterranean Romance coast paying lip service to either Romans or Goths (if not both) and being entierly surrounded by not that much romanised Berbers.