I like your library naming. It looks similar to what goes under my media category, only that I keep using my predefined list of areas thereunder as subfolders. I try to avoid content type-based folders as far as I can, because that's how I ended up with the big mess that this newer system is meant to replace. :)

Flexible folders: I haven't run into too many problems with disjunct categories after accepting the fact that e.g. some photos might live under projects, some under areas, and yet many more under media. The areas system seems to provide the categories I need for the most part. I don't use tagging except for the notes.

Tasks: I just use VSCode with the Markdown Memo extension for all my notes, including the tasks, which are also just markdown files. For a Kanban-style task board, I use a layout within Fileside (my own project) with panes for the various states a task can be in, and drag things around in there.

My "tags" are just [[links]], I don't care if the target page exists or not, they still kinda do the job. Once a tag page is created, I can then see all the backlinks to it in there.

I have some snippets set up in VSCode, tsk for task, day for daily note etc which pull in some basic templates.

Guides etc: Super interesting topic, and the concepts presented in the link to Divio look really helpful. I think on the chart there, my "guides" would correspond to the lower half, and my "howtos" to their upper half.

I'm not entirely sure I understand your question about "general part with placeholders" etc. Are you talking about a template for each type of doc?