The reason why they Hyorin sounds more live is because the microphone has a clearer sound than the attached microphones. If the others use a normal microphone, the live and dance will become more complicated and they will have to struggle extra difficulty.
Hyorin is the only one with a mic because the other three have special parts that require their hands. Soyu has her dance with the guy and needs both her hands in order to do the spin part. Dasom couldn't put on a hat and dance with her cane with a handheld mic. Bora is the only one who probably could have had a handheld mic since she throws the glitter with one hand, but she still wouldn't have been able to do the dance on her rap part.
Either they r really tired or it is there mics that make them sound like that but I'm pretty sure people in the comments cleared everything out I just didn't read them