Porting is much easier, yes, but keep in mind you'll need all the tools necessary to convert. I'd recommend using another armor as a base first, and then personalizing it from there. Making an entire armor set from scratch would be pretty difficult.

It's a lot easier to delete than it is to add, so a lot of people get started by actually removing parts and pieces of armor. Either way, it's going to be a lot of work to edit the models, and you better have some kind of experience with modeling & sculpting. I've never used nifskope myself, so I can't say for sure, but it's probably possible to make models in dedicated programs like 3ds MAX or Blender and import them. Making clothing and armor is pretty difficult, but it's not because of the engine itself. I guess what I'm trying to say is, modding is powerful in this game, but it's not necessarily easy. It's not the most streamlined experience, that's for sure.

I don't know about 'newbie friendly.' The engine is pretty janky overall what makes it so viable for modding is that just about everything in the game is open to modification, so you can make anything.

Fallout 4 clothing mod