I premise that I have an Elo score of 800. I'm reading a 7-book series by Garry Kasparov that seems quite comprehensive: it initially covers the general principles of an opening, then goes on to study the various endings, and then moves on to all the tactics, pawn structures, etc. In short, it is a complete series.
So far I have only read the first chapters on: general principles to follow in openings, checkmate with various pieces remaining. I already know most of the tactics and other scattered concepts, so it's just a matter of getting deeper as I continue reading.
However, having the feeling that I play openings randomly (while still following the basic principles) it occurred to me to start learning a couple of openings for white and a couple for black and understand them thoroughly by playing them. The problem is that I am totally stuck: both the series of books I have and many other books I have checked out merely describe variations of an opening by reporting what the best moves are. Taken individually, these moves make sense; the problem is that I can't find anywhere what the basic strategic plan of the variant is in order to understand it thoroughly. Let me explain. I started to see something about the Italian opening and main lines and some variants. Let's say the basic plan of the Italian game is clear to me, that is, piece development to castling quickly and targeting black's weak pawn f7. At this point, suppose we get into the gioco piano and, in particular, the variant of the gioco pianissimo (Just an example): after reaching this structure (After pushing the d pawn on d3) what are the strategic plans of black and white to continue playing? Where will white go to attack and where will black attack? What weak points should be attacked?
I can't find any book/video/site that explains the variants in this way; they all just come up with the best moves, but without indicating what is the strategic plan of black and white in making those moves, that is, what is the plan to follow once a particular variant is set up on the board. It seems pointless to me to study openings in this way, without understanding what is the plan to follow when entering a given variant and memorizing the best moves.
That said, are there any sources to draw from for studying openings/variants in this way? Or is this simply something that I need to leave alone for now because I am not yet able to understand it and first I need to deal well with all the tactical aspects and pawn structures and other things, continuing in the reading of the book series I have?
The fact is that I would like to learn at least one variant in a decent way, since I have the feeling that I play the openings in a casual way, simply respecting the general principles, but, precisely, I cannot grasp (or I do not find described explicitly) what precisely the strategic plan of that particular variant is, regardless of the best moves that then need to be made: if one understands the strategic plan, I think the best moves come accordingly. Do you have any advice for me?