First album of was indeed made by Tcha-Tcho style mixed with Tabu Ley's rumba-style. Back in those days they used to call Karmapa the new Koffi Olomidé. Being also Europe-based like him, former songwriter, etc. But it seems that he quickly wanted to get rid of that idenity, when he got the nickname "Le Prince la Rumba" from Tabu Ley and him seeing as his succesor. From then his music started since Temps de l'Amour was more like that of Vicky Longomba, but on a modern way.
Just compare Vicky's song Invocation to Somida of Karmapa
I don't know if he worked with Koffi Olomide. But it could be possible. Karmapa never said for who used to write his songs in the press. It's only when Papa Wemba died that he revealed that he wrote a big part of Phrase for him and other songs that Wemba would mix his songs with that from songwriters. In his interview with Ado Yuhe, he releaved that he wrote Kilimandjaro for Wemba and that it was the only song that wasn't modified. What I remember about Koffi & Karmapa, is that Koffi used to praise him alot in the press from the start of his solo-career in 2003 until that Tatiana Cruz left Karmapa. There was an interview that where Koffi jocked that he heard that there's a third Koffi coming, alluding to Karmapa (Wazekwa being the second Koffi).