Besides some words being integrated here in there with Arabic across North Africa, is there any remnants of maybe a sub vulgar Latin language still being spoken? Or did it all really collapse by the 700s? Excluding modern Romance languages themselves.
None that are known. There are a few sporadic hints that a Latin-derived language may have survived as a spoken vernacular in some parts of north Africa even as late as the 14th century, but there's no real concrete evidence.
Berber even now has a decent number of words that are (or are at least theorized to be) Latin/Romance loanwords — e.g., abekkadu, "sin/sickness", from Latin peccatum — so it's not unreasonable to posit a healthy amount of contact between Latin and Amazigh speech communities at least in classical antiquity, if not later. Whether that implies the existence of an actual Romance language post antiquity is mostly speculation, though.
The scholarly literature on this topic seems pretty sparse, almost all of the sources I can find only mention it as an aside to other discussions, but you might want to take a look at Vandals, Romans and Berbers: New Perspectives on Late Antique North Africa, Merrills (ed.) if you can get it.