I dont just base on fan club numbers but the actual demand for their items. I always buy from c-sellers. From my observation, Jennie and Jisoo photocards are sold out fastest, followed by Rosé and Lisa. And Jisoo's photocards in China cost the most (usually double the price of Lisa and rosé), while Jennie is almost on par. But Jennie ones are almost always sold out the moment they put on sales.
So my deduction is that the popularity/hardcore base goes from Jennie >= Jisoo > Lisa = Rosé
me neither lol I based on how they were trending, engagement and some popularity ranks on weibo + some chinese blinks I asked. Anyways, I don't think it doesn't matter lol Lisa is the most popular now. Jennie is pretty popular elsewhere so she still might do well.