So her name is in the Japanese style (Last/First) so her common nickname is Bae rather than trying to properly pronounce Baelz.

She's a fellow Aussie, and one thing you may not have noticed in the credits: She choreographed the entire video herself.
Just incase people don't understand: For the majority of this video its her and her back-up dancers in mocap suits doing this entire choreo. This isn't some animated movie. (Obviously the parkour breakdown was) When she debuted this song at her birthday concert in February, they did it "live" (not sure how live it was, but it was done on stage with the rest of the concert).

Baelz puts 'ratatata' is a few of her songs - probably because lore wise she is chaos in the form of a Rat.

Cover had a huge upgrade in motion capture equipment. Bealz was explaining that she changed the choreography from the most basic to fast movements and was able to incorporate them. She only complained that it didn't capture the movement of her butt very well (jokingly implying that she doesn't have a butt to capture).

japanese are very fond of turning sounds into actual words so it's very common for these vocalised sound effects to be shared between people

Ratatata is the machine gun sound and means nothing more than that though in context she's mimicking and calling out to losers or the downtrodden implying chaotic or angry and frustrated release of emotion 'Shout! Ratatata!' She then goes to flip the narrative in the following verse.

When she hits that visceral scream near the end on "We hit that high" she has stated that was a real scream of pain that she hit her arm while doing Mo-cap for the scene.

One of the things you asked about established lore. Much of the stuff you talked about are just anime tropes. People with animal ears and tail are a trope called "Kemonomimi" which is literally meaning animal ears. So characters that have a couple of features without going far into the "furry spectrum." Another one is the alternate personalities, this can likely be attributed to "Gap Moe (pronounced mo eh)." This is something that is like a departure from the original type of character traits they possess. Think the tall, confident, and loud, tomboy woman with defined muscles, but she puts on a dress and acts a little shy because of it. It shows an aspect of the character that no one knew they had.

Vtuber corporations are the ones more likely to have an established lore either for the generation (a group that debuts together) or for the company as a whole. Some don't though. Hololive does for the most part after the first couple of generations though.

At 10:16 that scream was her actually pulling a muscle, I forget which one, during the choreography. She liked the sound so much that they kept the take.

Very sad no one seemed to let him know this Vtuber, Bae, is also an Aussie. Thought he may have geeked out over that.

For the "putting on voices" thing. Yes near all Vtubers put on a cutesy anime voice when they start out but most drop it after about a month or so. This is because it's honestly hard to keep up a fake voice while streaming 5-10 hours ever single day. And then on top of that some of them doing are singing and putting on concerts. It's a real voice killer! To the point a couple vocal coaches here on youtube are getting together to come up with something to help Vtubers with this very issue.

For Hololive, each generation has lore develop around them either intentionally or along the way (usually a combination of both). Hakos Baelz is part of HoloCouncil, a group whose concepts were designed around different foundational concepts (time, chaos, etc). In her case, Bae is "Beelzebub", representing Chaos. If I'm recalling right, the company itself determines the identity and concept of the VTubers (I could be wrong though, and I have no doubt they work with the talents themselves in the process).

So happy to see you reacting to my favourite Aussie rat, the embodiment of chaos herself 😁 Bae thrives in plenty of different music genres, Psycho, Play Dice, and RxRxR being some of my personal favourites to showcase

Aye man, you know you can find the live version? In Hololive English official channel there is a live concert called Serendipity, in the free preview in part 2, we can see Bae (Hakos Baelz) singing "SNAKE EYES" + more Vtubers with their own lores that you can totally check (very talented girls ^^)

Edit: I have been subscribed to this Vtuber Company only for 7 months that they got me addicted to watch them everytime i got time 😅

In regards to vtubers and established lore of their character/avatar and overall design, it varies from person to person. I think that having a backstory/lore, especially with very recognisable physical features, such as animal ears, helps show individuality and generally makes things more interesting. There are plenty of vtubers with avatars that are human. I don't think it's a necessary a set of rules/guidelines to being a vtuber, it's just that these different elements put together, more often than not, provides more tools to make interesting content, interact with the audience, and sometimes leads to awesome fan work. Putting in references to lore in music videos for example, also tends to hype up fans who understand them. I'm so glad Bae got your signature fan opening!

It says something about many vtubers, including several in hololive, that they have had to go through surgery due to vocal nodules.
If you listen to how many hololive talents talked when they joined and compare it to today, there are clear differences that show many have given up on a fake voice as time passed.

Hakos Baelz has such an awesome style and I really love her voice!  Some other vTubers seem to put a voice on but she sings as if she was rocking a concert and this is just a music video. I love it so much!

Thank you for this reaction video DJ, and for always sharing the livestream videos so that we can all enjoy them <3 #HerdLove

Bae's signature karaoke song is Phantom of the Opera, you should definitely check out a clip of that! She's sung it a ton

Oooo I love Bae! not sure who suggested this but W suggestion :) Her dancing and singing go fantastic together :)

Nice one to start loving the Rat x) I recomment Psycho, it's a really good one too, also yeah the "ratatata" is because well, she's a rat ^^' the dices is also a recurrent theme in her songs because she's supposed to be an avatar of chaos.
She was doing a "character voice" at her debuts, but now she said that she just use her regular voice because she likes it better, she feels like it fits her character better, and also honestly people like it more x)

old comic books used ratatatat as a sound for machine guns, so it's often used in reference to that, in bae's case, she's also a Rat, so it makes sense. :P
Also, her fans are called "Brats" rather than just rats. :P

If you like this I would also recommend checking out Distortion by Moona

I would love for you to watch beastiez monster