A collection of different sources and guides that can help you.

• Substance Painter Export Settings for the Various CK3 Shaders
• Discord, Shader Pack for Maya
• WoW.Export, we don't mind using WoW assets if they fit CK3 style, so you may need it to export WoW assets. Here is Youtube Tutorial.
• Portrait Editor, a great tool to test and check in-game models.

• CK3 Wiki, 3d Models, explains how CK3 handles models, link possible tools, and EXPORTERS, this is important.
• The Great Big Guide to EVERYTHING Paradox Graphics, a very detailed guide, but it's made for HoI4 and Stellaris, but share many concepts with CK3. It will explain how you properties textures work. Using Blender.
• Youtube, From Blender to Crusader Kings III: complete process tutorial, shows how to stick the model to the character and make it work in-game. Using Blender.
• Don't go over...
  • 2500 triangles for on-map models.

• Clothes and legwear should have fat and dwarf blendshape meshes in the same folder as the main models.
• Check Warcraft-Guardians-of-Azeroth-2\.artist_resources\model bodies if you need a model for designing clothes and headgear.
• Don't go over...
  • 7500 triangles for clothes.
  • 5000 triangles for headgears.
  • 4000 triangles for capes.
• If you create a complex blend shape or animation for some race, consider splitting it into a few parts. Like instead of creating one blend shape for "orcish face", you create 3 genes: tusk, high nostril, long ear genes. This will allow using these genes in the future for other races and will add customization options.
• Male and female versions have different rigs. Transfering meshes from one sex to another (like making male clothes into female clothes), don't forget you have to change the rig.

We copy the vanilla saving style thus...

• The file should have one object with one mesh and one material. If the model is not a blendshape, you need a rig, a modifier with a link to the rig, vertex groups.
• Names:
  • Object: <File Name>
  • Mesh: <File Name>Shape
  • Material: PDXmat_<File Name>Shape

Images

P.S. It's based on Blender.

We copy the vanilla saving style thus...

• Models are in Warcraft-Guardians-of-Azeroth-2\gfx\models. There are subfolders for portraits, clothes, cloaks, etc. Portrait models must be separated from each other in folders.
• Portrait file names must follow this format:
  • .asset: wc_<Path>.asset
  • .mesh: wc_<Path>.mesh
  • Diffuse textures: wc_<Path>_diffuse.dds
  • Normal textures: wc_<Path>_normal.dds
  • Specular/properties textures: wc_<Path>_properties.dds

The Path is a combination of every folder name in the path. For example, files in male_cloaks\secular\western\royalty_01 are named male_cloaks_secular_western_royalty_01.

• .dds: DXT5 compression, with mipmaps