Is this a second or third-party source?

So there's a rabbit girl vtuber, Usatama Amyu, who posted this image to her Twitter; I thought it was cute so I uploaded it as post #7085970. She never actually provided an attribution to the original artist so I've been trying to figure out who the artist was, and I believe I've tracked it down to this Skeb request. (The artist also posted 2 non-watermarked versions on Pixiv.) Since it's a vtuber posting an artwork of themselves drawn by someone else, that makes it a second-party source, I think.

The detexted versions that Usatama Amyu posts on her Twitter do not seem to have a source anywhere else, judging by reverse image search, but, the original Skeb request was delivered as a Photoshop file - so I assume Usatama Amyu took that and removed some text layers from and maybe swapped around some facial expressions. Which would make it a... second-party edit?

On top of that, if you look at the original Skeb request, it was not actually requested by Usatama Amyu, unless that's an alt account (doubt). So she's neither the artist... nor the commissioner... does that mean it's really a third-party source and third-party edit?

Oh, and these other variants from Skeb/Pixiv - 1) do I bother uploading them at all when they have all these annoying text overlays in the way, and 2) if I do upload them... what is the parent supposed to be? post #7085970 is by far the cleanest and it's uncropped (compare the ear in the top left corner), but it's also technically derivative, right?

If I were to upload that image, I would still consider that source as a second-party.
The purpose of the second-party source and third-party source is to distinguish how close to the artist, or how official, the source is.
I assume that if that commissioner is not the tuber herself, then it is may be one of her followers who just shared the .psd file with her privately.

That makes the VTuber a 2nd party. Either she commissioned it like indie VTubers usually do or someone did it for her so she could use it commercially, based on the request.

Personally I don't post or approve images with large and obnoxious sample watermarks, but others might. I'd make the 2nd party image the parent in this case.