In general you're right.
I experimented for several hours.
If you are using Hanmen Next gen Skin and have an issue with a seam on the neck, then perhaps it will help you:
1. In the Material Editor, the
Gloss and
ExGloss settings should be the same for the head and body.
2. Then focusing
on the chin, not the neck
View attachment 3604654
View attachment 3604657
3. By changing the
SubsurfaceAlbedoSaturation, SubsurfaceAlbedoOpacity and
TransBase parameters, switching between the head and body, make the seam on the neck invisible.
After this is done, in 80% of the situation the seam will not be visible. The remaining 20% depends on lighting.