I'm curious about how "安源源源7号 / Anyuan No.7" makes their MMD models.
I've attached a video link and an image as an example of what I mean:

BiliBili
YouTube
(The examples I provided are from the creator's older works. Recently, this creator has been making videos using Koikatsu, and I am aware of that. However, I am specifically asking about the models used in their previous works, especially the ones used for MMD or Blender. I am also talking about the character model itself, not the clothing. I already know how they change or customize the clothes.)

Does anyone know if they:

• commission custom models from someone else?
• edit the models themselves?
• use one base body for every character and simply replace the head?
• Do they use any specific shaders, textures, or other visual effects to achieve this style? (Is it possible that they are using common MMD models but making them look different through shaders, materials, or other modifications?)
• or use some other workflow?

If anyone knows anything about their workflow or has any ideas, I'd really appreciate your help. Thanks!