you are right. extra is more different compare to other Congolese band since they have their own style in singing even atalaku. where did Petite Balaise go if you know. how many album he participated with musica? Petite Balaise had other alternative name?
one of the reason i always say that its because of extra musica that wenge had to step up and come out a more vibrant style(ndombolo)... you can feel the difference between plein feux (before extra musica nouveau missiles) and pentangone whenthey actually got impacted and even where obliged to add extra musica animation in thier songs... ( niema koko ..koko niema ) a pure kila mbongo signature . if you pay attention you will notice that the animation was already in nouveau missile back in 1993 and wenge repeated it in pentagone in 1996. so to me .. extra did not really copy wenge but impacted them.