Ironically, in most cases, more comprehensible than a really thick patois. It’s mostly a matter of exposure. There’s a huge African population in Paris, but genuine patois speakers are now few and to be found only in their respective regions.
Well the evil Parisians don’t even try to understand 
Um, again hard to answer as it comes down to the level of education the African has had - ie how far they went with their schooling and how much exposure they have had to French since then. Those I’ve seen subtitled would probably include nomads during coverage of the Paris-Dakar, fisherman or market sellers in documentaries, members of a crowd during demonstrations etc. Professionals ( politicians, doctors, those in the tourist business) are generally clear.
Interestingly enough, and pertinent to the OP, more than once when I’ve been talking to a French speaking African and had this exchange
“What other languages do you speak ?”
“Only English.”
"Oh, you don’t speak any African language ?
“It’s only a dialect.”
Said dialect on one occasion was Yoruba with approx 20M speakers worldwide !
I studied in France for a year and found the Africans I met to be slightly easier to understand since they spoke slower and enunciated. However this was in the university and they were speaking standard French.
I speak Spanish and Portuguese and while I could understand Catalan, it really is a different language. To me it sounded closer to Occitan.
Catalan is much closer to Occitan than Castilian, but how often did/do you hear Occitan?
By the way, Ladin and Friulian, the last two “dialects” on the list, are dialects not of Italian but of Rhaetian, along with Romansh, spoken respectively in parts of Trentino-Alto Adige and Friulia-Venezia Giulia. Rhaetian is sort of the redheaded stepchild of the Romance language family, nowhere a national language and official only in Graubunden canton of Switzerland (where Romansh is fighting a rearguard battle).
I was in Provence and saw it in writing on the street signs. The library there had a few books in both languages and I took a look to compare. I don’t think I heard anyone speaking it other than a few old people.
Frisian is as much a ‘sister’ language of English as Dutch and German are. It certainly is not close like all the different forms of French and Italian that are listed.