Nayeon: Music + Modeling Nayeon will likely have the most successful solo career out of Twice. Pop! proved her popularity and she has one of the larger solo endorsements(Biotherm). She just needs to solidify herself as a soloist with some more comebacks and she can become a very big solo artist. I also think she will open a youtube channel.
Jihyo: Music + Modeling + Acting. Jihyo is next, I think she will have the second largest music career out of Twice. Not as big as Nayeon but still successful. Jihyo is one of the less popular members in Korea so her music probably won't chart amazingly but she will be celebrated as a vocalist. Jihyo spend some time at JYPE learning acting while she was a trainee, so I can see her doing that. Surprisingly, I can see her as a radio host. I don't know why I just get that vibe from her.
Sana: Music + Modeling + Variety. Sana is one of the more confusing members for me. When I was thinking about her future solo career, I realized that Sana is Twice's secret jack-of-all-trades. Modeling, variety, music, hell even acting. I can see her doing all of it. Personally, I think she will focus on modeling and variety the most and drop music every once in a while. Also, youtube channel.
Mina: Modeling. Despite Mina having very actress-like visuals, I can't see her as an actress. She also hasn't shown a huge interest in solo music(from what I've seen, I can see some OSTs in her future though.) However, I can definitely see her diving into modeling. She's also the only member in the j-line I could see spending most of her solo career in Japan.
Jeongyeon: Acting + Music +Modeling. I think that Jeongyeon will go into acting, she's shown interest before so it'd make sense. I can also see her doing music, but not focusing on it too much.
Dahyun: Variety + Music + Modeling. Dahyun will become a HUGE variety star, I can sense it. She always shines when Twice goes on variety, so I can see her going the Mijoo route. Dahyun has also shown interest in music multiple times, learning two instruments and having the most writing credits behind Chaeyoung and Jihyo. So I think she will be like Sana, dropping music occasionally while focusing on other things.
Momo: Dancing + Modeling. I can't see Momo going solo, however, I can see her going on various dance-based shows and also doing modeling. The only time I can see her doing music outside of Twice is maybe as a featured artist in someone else's song as a rapper
Chaeyoung: Music + Modeling. In my opinion, Chaeyoung will mainly focus on music, I can see her style of music is very similar to Sunmi's current style. Chaeyeoung is one of the members with the most solo potential. However, since she is one of the less popular members both internationally and in Korea, she will be more "underground"(well as underground as you can be as a member of such a huge girl group) Still, she will be successful. And I can't wait to see what she will do when she's given more control over her image and sound.
Tzuyu: Modeling. I really can't see Tzuyu doing much else, maybe dancing, but that's about it. She is one of those idols that shines the best in a group.