I don't know which mod that'll suit type 3 body, since I don't use that mod, but to answer the removal neck seams. No you can't. It's Bethesda's stupid way of creating characters back in the day. There is a way to hide it though.
Distributed Necklaces and Chains (JIP LN NVSE) (DLC and TTW)
https://www.nexusmods.com/newvegas/mods/56198