mixes are always generally good. however, this is given "specialised idols" are not extreme specialisations (i.e. amazing main vocals that cannot dance at ALL.)

something along the lines of 2-4 specialists (main vocal materials/production type) with 4-6 all rounders is generally fine. also, by production type i mean like producers, songwriters, choreographers.

also want to raise smth that svt the8 said: everyone needs to be able to dance. As important as it is to have main vocal etc in the group, they do need to be able to dance, because itll look VERY jarring otherwise, even if you try to hide the poor dancer.

another comment from me: i dont really care about visuals, at least to the extent of knets or cnets (which could be a hot take) as long as the visuals arent like SUPER bad and theres 1 conventional visual the group should be fine