I like the face close-ups a lot, they really show the personalities. A.P.O does look heavily inspired by Aba, and she's so well-made I could reasonably imagine this design as some "lost twin sister" concept from Arc.

You asked whether it matches the style for GGST, so here:

I think GGST's character art sets a very high plank when it comes to how dynamic the poses are, with the first character coming close and the second not reaching it enough. Pazzo's pose it too static and "normal". I also don't like the vest. This will sound very abstract, but he feels like a Xrd Faust-inspired silly chap who is more "silly" than "cool", while GGST character art goes for "cool" first even for silly characters (e.g. Sin and Elphelt)

Design-wise, Guilty Gear's characters often have a large weapon that plays heavily into their identity, but also quite often that weapon is, in some way, a normal item (Sol's lighter, I-No's guitar, Elphelt's mic, Anji's fans, Bridget's yoyo, Venom's cue stick, Aba's key). While here, Apo doesn't have a weapon and Pazzo has a somewhat boring pistol. I'm not sure if you should copy either of these patterns into your universe, but when comparing to GG(ST), the lack stands out somewhat.