>>20151104Elira has this fujo onee-chan gfe thing going, and it's better than it sounds. She has trash taste but she's still lovely. Known for her cozy zatsudans.
Pomu is a cave-dwelling terminal weeb shitposter. Has a lot of fun doing everything. Probably the best starting point overall.
Selen is a gamer tomboy gremlin. Good for shooting the shit with. She's not super social so you'll probably get the least exposure to her through collabs.
Rosemi: daughter. Innocent with a mischievous streak.
Nina: pretty divisive since she tends to dominate collabs and produce bountiful cringe. I haven't watched many of her individual streams but she seems to be better there and also tends to play more niche stuff not many other vtubers play.
I don't know enough about the others to really describe their content. nijiEN tends to thrive on collabs, so I'd suggest just picking a few to watch and you can quickly get an idea of what everyone's personality is like.