The "weak" raiders usually go in small groups and wear black leather jacket only. Men wield 9mm Mausers, while women use spears (those are the only weapons they use).The "strong" raiders tend to be found in bigger groups and have more varied looks (bald guy in leather armor, for example). They also use better and more varied weapons. These are not really raiders, but actually the mercenaries who are payed by Mr. Bishop from New Reno. These are the "Raiders" you can join (but they'll shoot you in random encounters anyway) and according to FOnline, they are the Khans but if you stick to Fallout 2 this is false, since the Khans moved to Vault 15 after Garl was killed by the Vault Dweller.
So... you're saying the southern raider base isn't home of the Khans? It wasn't even in FO2, so no way it's run by Bishop's mercs.
The FOnline Khans aren't really exactly the same like in FO2.