I don't know your specifics, so I'm going to reply with what I've learned about learning:
I found reading a textbook, and typing notes into a dumb markdown file with the textbooks name is good enough. Typically: definitions, quotes, and personal thoughts while reading. Did this for stats/comp sci/etc. Obsidian + markdown worked for that, even without plugins. Being able to text search is useful, which is why I don't hand write.
Anything beyond that you have to be cautious about paralyzing yourself from trying XYZ PKM.
Theres a quote from stephen king that goes somewhere along the lines of "during first draft don't try referencing or fixing grammar because it breaks your train of thought". I think similarly, when learning something, choose the thing thats most out of the way (usually the simplest) that is least likely to break your train of thought.
In terms of tracking how much you're learning, I'd be very very slow and incremental in what tooling/methods you pick. For me, I just trust myself after reading/notetaking a textbook. Usually homeworks get very easy which is a good sign. Being able to explain what I learned to someone else is a good sign.