Should I in general always unwrap my entire object in one UV map? I have difficulty creating a normal map for a sword and I have the feeling it might be caused by how I approached the project.

Instead of making the entire sword out of a single cube I started with one cube for the blade, then added a cylinder for the grip and so on.
After I was satisfied with the general form I unwrapped each single mesh, instead of making one unwrap for the entire sword, and gave them textures. I proceeded with copying my sword so I could have one low poly object and one high poly object. On the high poly object I added details with sculpting again for each single mesh of the high poly object (grip, blade, etc).

In order to bake both objects together I now need to overlap them perfectly.
But because each of the two swords consists of several independent meshes this is quite hard. So I joined the meshes together for each sword. 

Now I could easily make them overlap. But after I bake them together I only get a normal map for the grip and not for the entire sword.
So I think I need to make an unwrap for the entire sword instead of making them for each mesh. Should I in general always unwrap my entire object in one?
But that makes texturing so much harder when I use different textures for each part.


Even my low poly sword has 15000 vertices. I once read that high detailed characters in video games have around 30000 vertices. So 15000 sounds like quite a lot for a single sword. But is a high number of vertices always a problem?
For example I can insert vertices on a flat surface as much as I want without changing the amount of detail of the surface. It is still a flat surface with four corners. So are these additional vertices a performance problem when I later use the sword in a selfmade game?
I also tried to make a human. I watched some tutorials on youtube where they sculpted the entire face and body, but is that actually how you do it for a video game?


My human had over 70000 vertices after I did it that way. Sounds like way to much.

So to sum it up:


Should I always make my objects a one mesh and should I always make one unwrap for the entire object?
Are a lot of vertices a performance problem even if they don't add more detail to the object?
Should I create characters by sculpting?
A couple of screenshots would go a long way in helping you explain your situation.

I'm going to guess that you have a lot of unnecessary polygons on your models. If you want your game to run smoothly or not require excessive computing power, you're going to want to optimize your models by reducing the vertex/face count.

If you insert a vertex into a side of a quad but don't do anything with it, this is no longer a quad. Extra vertices can cause shading errors and other problems when using modifiers down the line. Removing these extra vertices also helps optimize your model.

As far as the more specific questions about the game asset workflow, try searching up for "Blender game asset creation tutorials." They'll be much clearer.