Which nightsisters? Which raids?

Witherox22

https://swgoh.gg/p/675525135/characters/

i will upgrade 5 of my nightsister to 7*
Which of them?

Talzin, Zombie, Daka, Ventress (will Zeta her unique), which 5th one ? Talia, Akolythin ?
Which raid i can use them ? STR which Phase ? strategy?

Witherox22

Talzin or ventress Lead ?

Naraic

Ventress lead can solo pit, talzin lead can do well in tank but ventress as part of an abc team is even better, talzin lead for phase 3 hsr and ventress lead for phase 4 hsr.

As to a 5th you probably need multiple ones for different game modes. I'd level up talia first. She is best for sith raid phase 4.