I’m confused on what you are asking. Are you asking when people bake PBR textures for their characters, or when they assign multiple materials to a character?
I am going to assume you mean when do people bake PBR textures. If you are meaning something else, feel free to ignore what I wrote below and my apologizes for misinterpting the question.
I am by no means an expert on game development or 3D modeling but here’s what I know from what I’ve read from other game developers and from my own experience:
Assuming you are using a work flow similar to the following:
Blocking, UV mapping (sometimes after sculpting), Sculpting, Retypology, Potentially UV mapping again, Rigging (and animating), Exporting.
I have noticed that most people texture after the sculpting stage, and then bake the textures on to the final model.
They do this so they can bake the normals and ambient occlusion maps along with the textures, streamlining the texture creation process.
Another advantage of texturing after the sculpting stage is you have really cool models with PBR textures for your portfolio. If you are working in a team there is also the advantage of being able to send the sculpt to someone else to retypologize while you (or someone else) make the textures.
Personally, I rarely sculpt my characters and instead model my characters without any concerns on vertex count. I then make materials with solid colors to get an idea of what I want the final model to look like, and then I retyoplogize the model. Once I have the retypologized model, I then UV wrap and texture in something like Substance Painter or Armory Paint.
This method makes it where you can not easily export the detailed normal or ambient occlusion maps. Personally I’ve never been bothered by this, but I generally make fairly stylized models.
Another disadvantage is this workflow is harder to use if you are working in a team, but since I work solo it’s never bothered me.
One advantage is it’s a little easier on older computers since you are not texturing on a vertex dense model. Finally, I personally find this workflow easier than the more traditional workflow as it just seems to work better for me.
That is pretty much all I know on PBR texturing.
I would highly suggest looking at some tutorials for making game assets in whatever program you are using and experimenting to see what works best for you. I have found that optimal asset workflows are different from person to person. I had to make my own workflow because none of the ones I found fit nicely for me personally.
