I have to agree that Seiko's uncontrolled wailing is what I enjoy most about her (I this say while my favorite song is and probably forever will be Midnight Seijun Isei Kouyuu). It's not something you can expect everyone to like, though, especially if you go in to listen after hearing her come up as a recommendation somehow for those who like an artist like Ringo.
They both have their fascinations with different facets pop music and how to express that in their own way, but even their musical backgrounds and influences seem so different. I honestly feel like the association is entirely based on that Shouso Strip homage/parody cover she had...
One thing about Seiko for me though is that a lot of artists who can't necessarily sing tend to fall into the same vocal style? Like, I listen to hirone-chan sometimes, and she does a similar wavering-wailing/fast talking thing while standing with her instrument. It kinda reminds me of when Ke$ha broke and I couldn't tell which songs on the radio were her and which were similar-sounding one-off artists
Also, kinda unrelated, but I don't get why everyone says Zombie Chang is so cool. Like, she seems chill and cool and her music is nice, but it just kinda reminds me of college kids...? I guess that's cool tho. Ppl in college are chill and cool, and she seems like she's enjoying herself even though her name gets pronounced wrong. If there is something definitively cool that she has done, please do let me know though
Also, BiS fans are definitely wilder than Oomori fans last I checked. It was like being stuck in a raging whirlwind for like 2 hours. I've never walked out of a show covered in so much sweat that wasn't my own, and I'd lost my voice even though I don't remember screaming
Also, I don't see the problem with idols having a lot of their music (though not always lyrics?) written by others. If you have songwriting talent but not the voice to bring your work to completion, then why not?
...But man, I really miss BiS...