Most of Koikatsu's zipmods work in Sunshine, but I should also mention that many of the cards converted for this version often have minor bugs that you can fix manually. Some cards load without the body alpha mask (you'll see the bust showing through the clothing in some cases), and even without the alpha mask or textures on clothing and accessories.
But you can find everything on this page:
https://plugindatareader.maki0419.com/ Where it allows you to explore the cards' metadata.
Honestly, I don't know how to explain it without being redundant, so I'll just share my directory tree with you.
I clarify that the same order is used in both Koikatsu and Koikatsu Sunshine.
Koikatsu
(or whatever the folder containing the game's executable file is called)/
├─ BepInEx/
│ └─ plugins/
│ ├─ [Plugins.dll]
│ ├─ [Plugins for gameplay]
│ └─ [Preferred plugins]
│
├─ UserData/
│ ├─ chara/
│ │ ├─ female/
│ │ │ └─ [Cards.png]
│ │ └─ male/
│ │ └─ [Cards.png]
│ ├─ coordinate/
│ │ └─[Clothes/Outfits.png]
│ │
│ ├─ studio/
│ │ └─ scene/
│ │ └─ [SD/Scenes.png]
│ ├─ bg/
│ │ └─ [Backgrounds image.png]
│ ├─ coordinate/
│ │ └─[Clothes/Outfits.png]
│ │
│ └─ cardframe/
│ ├─ front/
│ │ └─ [front-card.png]
│ └─ back/
│ └─ [background-card.png
├─ mods/
│ ├─ Sideloader Modpack/
│ │ └─ [Modpacks -
DON'T TOUCH THIS MODS]
│ └─ [zipmods or Mymods/ folder]
│
├─ CharaStudio.exe - Charastudio executable
├─ Koikatsu Party/Sunshine.exe - Koikatsu executable
└─ InitSetting.exe - initial setting (Image quality, resolution, disabling or keeping rimlight, or auto-positioning feet when wearing heels (although I think that's no longer necessary in Koikatsu Sunshine); etc).
This is an overview; as you use plugins like BlendShape, take screenshots/renders, or save poses in CharaStudio, specific folders will also be created in UserData/ 
