For making faceted models appear smooth, use the normal smoothing. The normal smoothing and mesh smoothing are different things.
The mesh smoothing is a realtime GPU based sub-division. Manual page:
https://manual.reallusion.com/Character-Creator-4/Content/ENU/4.0/15_Tessellation_Displacement/Tessellation_for_Objects.htm
Instead of improving CC Standard characters conversion routine to Humanoids (for further customization) RL does everything possible to mess things up with every update.
I used to Export a Standard CC character, import it right back as Humanoid and get AT LEAST all the textures intact as PBR (I am not even going to mention THIS). That is no longer the case. Metallic, Roughness, AO are no longer going through! Why??
I tried an alternative approach - converted to Humanoid with Optimize and Decimate > Custom (I rarely use it). First, Convert button is not available until you remove some options. I did uncheck 5 toes bones. Conversion went fine and even body materials converted to SSS (although Eye Occlusion and Eye tear-line are gone - really bad!). Exported and imported back and got slouchy shoulders and obviously Metallic, Roughness, AO are no longer there.
Tried with Blender Pipeline, got all textures (although some parameters are not right and character is all shiny). But slouchy shoulders are still there…
How do we supposed to customize characters with this?? 
@4u2ges - Thank you for the feedback. I will pass this on to the dev team to review. I’ll update again after the dev team have had time to check the issues you mention.
