ObsidianMD

Yes sure! For your first question, it depends on the source, for example a book or a paper usually is a note because i like to resume or quote interestings idea or discoverings from them. Blog posts and news rarely are notes but usually they're put at the bottom of a note or link with title or one-two line description.

Books, video essays and so on are located inside a directory of resources. I usually add these resource notes as additional sources at the bottom of the topic notes, and/or quote what I find interesting fron the source.

Every note in my vault is tagged, this helps to find "hidden" connections between notes. As said before, not using systems like atomic/evergreen notes with strong atomization of content, full text search is essential for retrieving in my system. I use different vaults only if I need a strong separation between content, for example I have one for study/work, one for more intimate and general purpose stuff and one for preparing DnD campains.