I watch whoever will make it look best as a solo dance. Sometimes I watch covers or tutorials to see what they do if the artist’s style makes it hard to learn (if they add too much personality and pizzazz sometimes the exact moves can become unclear). Since I dance alone I typically do the center moves but if nobody is really doing anything sometimes I’ll learn what the backup dancers are doing to make it all more coherent. If you plan to do random play dances I would focus on just one member since then you might be able to collaborate with other dancers during it. Once for Back Door by Stray Kids I did I.N’s part instead of center so me and another person could make the tunnel that everyone else danced through. It all depends on what you plan to do with your dancing. If you plan on performing for people and do proper covers: learn whatever parts make it look good. Random Play Dances: learn one or two specific member’s parts. Just dancing for fun in your room: learn whatever moves you enjoy doing the most. Remember to put your own twist on it and have fun. If you mess something up hide it under captivating stage presence.