>Are these vtubers popular in Nijisanji or overall?
Yes.
Himawari is one of their most subscribed streamers. She's kinda naive and not exactly the most academically gifted to be kind, she likes eating and she's secretely a Ludicolo. She's as bright and energic as the sunflower on her hair would imply and a total sweetheart. She has a surprinsingly varied taste in games . She currently taking a break to visit family that she hasn't seen since the start of the pandemic.
Sasaki and Shiina also very popular and Sasaki would be the most subscribed if she didn't take a break for a year.
Sasaki is a technically a delinquent - she often "picks fights" with and "bullies" other members, but it's good natured ribbing. She's a nintendo addict (the afore-mentioned break was literally her quitting unitl her company secured the rights to stream nintendo games). She speaks with an accent with strong hints of being from Kansai. Sasaki can be both incredibly kind and incredibly brash, but she's ultimately a sweetie - she's very close to her family, she treasure's her brother hand-me-down Nintendo 64 nearly crying on stream once she thought it broke, and she talking about the passing of her father was extremely touching (and showed character, she disabled monetization when talking about her father because she didn't want pity money).
She's also a sumo wrestler not really, her retirement and return coincided with the the inverse of a famous sumo wrestler, the internet ran with the joke and it made national TV in Japan and has a cat.
Shiina is the smartest of the bunch but the's also the laziest - has been said that she ghosted friends meeting offline more than once because she woke up late and gave up going. She has good content but her best is probably collabs, she really plays well with other people. Right now her content is a rotation of collabs, Apex and Nintendo. She won Nijisanji's baseball tourney and have her likeness turned into a skin inside Namco's Power Yakyuu Pro Baseball 2020.
Shiina has a stronger personality and meshes well with more "troublemaking" members of Nijisanji, she's also known to have been a force fighting for the improvement of working conditions inside nijisanji in their early years and is known to be a very supportive senpai behind the scenes. She's also a fujo and a thot.
They all debuted under the uni Nijisanji Gamers 3rd generation and are friends to some degree. Sasaki is very close to both Himawari and Shiina, Himawari and Shiina don't interact as much as their circle of friends don't intersect that much besides Sasaki, but they seem to get along very well in group collabs. It's not uncommon to see they perform together in Nijisanji concerts either as Sasaki/Himawari and Sasaki/Shiina.
