I am right in thinking that C# can be used completely in Unity to create a project from scratch?
Meaning by using that I can just use code to create a game, instead of the copy/paste of items and such
You can do a lot in Unity with C#... if you know how.
Now, I am not sure what your question here really is.
If your question was if you have to use the editor:
Unity is just a tool that takes your input (scripts, 3D Objects, Sounds, ...) and builds an executable game out of it. How you structure your project, is completly up to you.
Of course, Unity was meant to be used with their Component-based architecture: You use the editor to create a level by placing 3D Objects, assign physics compoents, and in the end write behaviour scripts attached to the objects in the scene to get things moving.
But you don't have to. There are multiple people building their Unity projects in a completly different way.
For example some people will create scripts, or maybe even c++ Programs (yes, you can run them from a Unity script... You just can't open and change them in the Unity editor), that will generate stuff on the fly. They will place your mobs or other level objects, they might generate completly random levels, and so on.
Here, the code in the C# or Unityscript script or C++ Program will create the levels needed for the game, without creating them in the editor.
Of course the editor is still useful for some tasks. Importing 3D Objects and Textures for example.
If your question is if you can write everything or if you have to copy and paste:
Of course! That is the ultimate goal of every tool like Unity to give you the ability to write your own code and come up with original ideas nobody else has thought about.
But don't be afraid to use the occasional sprinkling of some copy-pasta code when you get stuck on a problem. Most professional programers are masters of the arcane arts of Google-Fu... its part of the secret to their awesome code (because to become good at something, you will need to learn from others first).
The good thing about an Engine with a huge community like Unity is: if you want to code away on your own, you can. If you get stuck and need to get some help, its always just around the corner.
If your question was just about the way you place Objects in the Scene in the Editor:
I think even in some of the most basic tutorials you will learn how to instanciate a prefab.
What "Instanciating a Prefab" means is: You have a preconfigured object (with physics, 3D Model, attached scripts) and place it somewhere in the running game.
How you create your prefab is up to you. Easiest is probably in the editor with drag and drop, you could of course also do this in code.
Yeah I was basically asking can I code from scratch and was asking what language was more worthwhile to learn for it, of course there would be some things I'd have to google and use from others.
But yeah I basically wanted to learn a language and eventually code a project, nothing big or fancy