I have tried a range of beauty and cosmetic mods to improve npc appearance. I keep having problems with the faces not matching seamlessly on to the bodies. Around the neck and shoulders you can see the joins. Is it possible to correct these issues so that there are no problems where the face and shoulders meet? It seems to happen with many cosmetic mods. Thanks.

As far as I know, this bug is not possible to remove. There are some beauty mods that try to reduce it, but you will still be able to see the seam. I remeber seeing a mod on Nexus that puts a permanent necklace or tattoo on your neck so that the seam is not visible (something akin to what DragonAge does if you are familiar with this game).