Google plus the internet is your second brain and is the optimal approach for almost everyone. This heavy approach seems like make work that will waste time, and the data will rot, leading to calcified and inaccurate knowledge.
1. Public (if it's non-public systems, information, etc. that you are learning then Google can't help you). 2. and either shallow or of one of a small subset of areas that has in-depth discussion online.
There are plenty of situations in knowledge work where Google will not cut it.
If the knowledge is already in the documentation or a book, why should I keep a copy of that knowledge elsewhere, in yet another format?