I've always used TextWrangler/ Notepad++ to develop websites from scratch. I'm now coding what I'd say are very advanced websites this way.
I want to know if it's efficient to do things this way and whether I should learn DreamWeaver and use that
I use Dreamweaver, basically because I'm a designer not a coder. I find it useful to use Dreamweaver, because it has all the tools you need to create a website. Dreamweaver has the ability to be a WYSIWYG in the "Design" mode, but you can easily switch to the raw code and mess about with the code. Which is what I tend to do anyway.
Dreamweaver isn't a cheat way of web design, it is a tool. Much like a pencil and paper would be to an artist, or a hammer to a joiner. It's not what is used to create a website that should be ridiculed or the designer who uses Dreamweaver should be abused. But in fact the website itself, and the application of web design skills/knowledge.
Dreamweaver has it's own project file system, so you know exactly what is in your project and what isn't. You can also see all the external files that are linked in one HTML file, such as a JavaScript file. You can swap between the source code of the HTML file and the external file source code, with one click and with no other open "windows".
Dreamweaver is quite easy to learn (in my opinion), and should at least have a fair trial run.
If I were you, I would download a trial version of Dreamweaver, and try it out. I hope I've helped in some way.