I didn't agree with the author, per se, either. I do appreciate taking in facets when approaching a new design.
I use nerdtree on a left split, and I divide that split horizontally with a Buffergator split. It gives me a nice GUI-like strategy that accommodates a few open buffers or many. The buffers-as-tabs metaphor (ala Sublime) fails when many files are open.
I have yet to gather a nice way to open multiple Vims, one of each 'project'. I think it would be superior, since it would (actually) manage the 99% reason for opening so many files. (I still would always use Buffergator to manage open bufs)
Drawers are my my common dilemma. I do use them alongside splits and will only be 'going deeper' on that one. My most common drawer is Unite.
The most common issue is with permanence. I ack for files, string, tags, etc and realize that I need to explore several to find what I need. Sometimes I know in advance and switch to another window (tmux, or osx terminal tab) to run the ack. Then I can send individual file paths to my vim-server name to open them (I know some flexible naming call would let me open a vim for each project...:/)
Often I don't know in advance how perm the search results need to be. Either way, I cannot select and auto-open the results as with a Unite drawer.
BBEdit has this solved well; it opens grep results [that span the file tree] in a new window. That window has natural permanence, and is integrated ala unite. (Unite is better since I can re-run, refine, sub-search, and format (colors).)
I like your idea of collapsing windows to a one-character width. If this was done with a unite drawer then I could re-expand it later since its holding the results of the last action. Actually, it 'grounds the metaphor' that the Unite search 'history' is a Thing, and that I could go back to the results of previous searches / actions. This may be in Unite now, for all I know.
I'm currently experimenting with whether I want a tag list (from the current file) to be a mostly-permanent split, or a drawer. I lean toward a split. I'm using Tagbar but may switch to taglist.
And like you, switching nerdtree for netrw is greener pasture that may not be a mirage.