Doom Emacs has a hideshow minor mode configured to work in a similar way to Vim:
z-c closes a fold
z-m closes all the folds in the buffer
z-o opens a fold
The question is - what is (are?) the best ways I could look at an overview of my project and/or current source file. By overview I mean a list of topmost names, and such.
I see. I use imenu for that, I guess this is the traditional approach, maybe there are better ways to do it. Using imenu you add some comment regexp and then in a source file you can create sections that you can reference using imenu.