No problem, yeah for the neck seams, I have not been able to figure out what is causing it. You don't really notice it much past the character creation screen, mostly because the lighting and everything is different (along with your armor and such covering up any seams).

The default hairs have mostly been fixed with the Vanilla Hair Tweaks and a few other hair mods on the list (UWE also has some hair tweaks/mods integrated in the overhaul).

Unfortunately I'm not very good at 3D modeling or I could probably try to fix them up some more. I don't really use the default hair styles too much, as they do look kinda strange compared to most other hairs on the list lol (there's around 200ish hairs total. The ones earlier in the selection tend to be the newer/higher quality hair types, 1-30 or so, same with faces)