I need help with feixiao.

Hello, I am planning to pull for Feixiao. I currently have every harmony unit and aventurine e0s1 in my account. When I examine some teams seems like Moze not working properly with Feixiao and this left me deciding whether to pull topaz or not. Even if I'm going to pull for topaz, I don't know if I should look at its bis lc or/and e1.

Also, I plan to leave Feixiao e0 for now, but since I have Dr. Ratio's bis LC, I don't know if I should pull for Feixiao's bis LC.

Finally, some of my friends say pull for Robin E1 instead of topaz, how logical is that?

I would be happy if you answer my questions. Thanks a lot.