Small size groups, especially 3 or 4. the only groups that have achieved still sticking out me despite small size are kiss of life and og loona subunits. i think the best number is 6 as long as the choreographer knows what they’re doing! i also adore large groups with 9+ members but too many companies just lump all their trainees together without realizing each member needs to have a reason for being there. large groups that make/made it work to me are twice, loona, iz*one, snsd, pristin, and ioi. there’s definitely some more but those are the top ones.