The accent you were hearing from Jelani is Carribean-Cockney. The main traits that separates it from something like the African Cockney black accent is the speed with which one speaks it (faster) and the more monotone delivery of it but also there's much harsher enunciation of the consonant that ends words.
they both vary how they say 'th' but Carribeans will go more for 't' while all other cockney variants aim for 'f' or 'v' sound.
Carribean-Cockney says this:
'How's tings goin' fam? You keepin' well 'n' dat?'
Whereas African-Cockney says this:
'How's you? You healfy 'n' okay?'
It's not just the slang, it's the delivery,
The best way to show you the difference is to give you an example of two rappers who have a Ghanaian-cockney (Stormzy) and Nigerian-cockney (Dave) accent to contrast with the Carribean-Cockney from the song I just showed you:
Big Zuu spoke more straightforward Cockney and has Lebanese and Sierra Leonian roots.