Do That Openings "Fit" Together?

1900 is a pretty high level to be asking this basic question.
Not really, no. There are systems like the Colle or Hedgehog and there are openings like the French. You could aim to get a French-like structure out of every opening, a lot of French players do this and it's a reasonable strategy. But it won't work for all openings and your opponent doesn't have to comply for most of the others. If you prefer the French but can play the QGD there's no harm in playing 1. ....e6 to d4 to give your opponent the option of the French. But the QGD is completely different to the French, similarly the Slav is usually completely different to the Caro-Kan.

1900 is a pretty high level to be asking this basic question.
Not really, no. There are systems like the Colle or Hedgehog and there are openings like the French. You could aim to get a French-like structure out of every opening, a lot of French players do this and it's a reasonable strategy. But it won't work for all openings and your opponent doesn't have to comply for most of the others. If you prefer the French but can play the QGD there's no harm in playing 1. ....e6 to d4 to give your opponent the option of the French. But the QGD is completely different to the French, similarly the Slav is usually completely different to the Caro-Kan.
Yes, I understand your point. And I understand that the QGD and the French are different openings with different strategies. My aim taking these opening choices is confidently have a sound and good answer to 1.e4 (French), and a sound and good answer to 1.d4 (QGD). For White, I just take the London System because it's another different type of game (and, "they" said, easy to learn).
They are essentially different? Yes, right? So, better for my chess! I'll have to study more, but my general chess understanding will be more comprehensive.
So, in that way, that openings does not fit together.
However, we have to answer other strong moves, too. I'm just asking if I will get similar strategies/pawn structures related to French or QGD when my opponent plays something different, like 1.c4, 1.f4 or ever 1.Nf3.
About this question be to basic for my level, well... actually I just play my openings until now following the opening principles. But now I think it's time to start to play some theoretical openings in order to play more complex chess, aiming for the 2200.

Nigel Short has combined the French and the QGD for a lot of his career. They seem to me natural companion openings, both based on a light-square pawn chain with the consequent problem of the QB, both accepting an initially cramped position and aiming to free it with later pawn breaks, especially c5. The London is a bit different, with a dark square pawn chain and the QB outside it, but it still has something of the same feel, with a basically solid position and the hope of injecting some dynamism later. So I think they go OK. Incidentally, after chopping and changing my defences for years, I am now trying to concentrate on a similar matching pair, the French and the Stonewall Dutch.

Nigel Short has combined the French and the QGD for a lot of his career. They seem to me natural companion openings, both based on a light-square pawn chain with the consequent problem of the QB, both accepting an initially cramped position and aiming to free it with later pawn breaks, especially c5. The London is a bit different, with a dark square pawn chain and the QB outside it, but it still has something of the same feel, with a basically solid position and the hope of injecting some dynamism later. So I think they go OK. Incidentally, after chopping and changing my defences for years, I am now trying to concentrate on a similar matching pair, the French and the Stonewall Dutch.
Thanks a lot for your answer! I will look for some Short's games to get some ideas.

I am looking at the French openings and I don't see how c4 is played.
In the Advance variation, e5 is played and then c3 usually. In the Winawer, Bb4 pins the knight on c3 and the c pawn is still on c2. In the French Exchange, the e6 is no longer there, removing any LS chain. In the Tarrasch variation, I am seeing c3.
I am not seeing the connection between QGD lines and the French. Can someone post a game to illustrate how these two openings can be treated similarly? I would have thought the Caro Kann would have been the "sibling" French opening for black, not the QGD.
Hello, Guitar Philosopher! Here is the deal:

If you like the ...e6, ...d5, ...Nf6 setup then perhaps you would be interested in playing the d4, Nf3, e3 Colle setup. In the past the Colle wasn't considered a stand alone opening, but a recent book titled The Modernized Colle - Zukertort Attack uses both c3 or b3, depending on black's defense.

Well, two defenses that remind of each other is the Hanham Philidor and Old Indian. Use 1...d6 against everything. Both defenses are considered to be somewhat on the passive side, which to me has been discouraging playing it early on when I had not studied the book well, but maybe there is something to be said for playing/learning their similar structures and middlegame plans over and over and over again if one is wanting to get out of massive theory. A book came out in 2019 titled Side Stepping Mainline Theory, it is about playing just those two defenses, and also about playing that structure when white.

You make the same common mistake that many players make.
The French and QGD do not play the same at all. Nor do openings like the Pirc and Kings Indian.
What must be realized is that all you are looking at are Black's pawns. You need to be looking at ALL pawns!
Black has the same pawn layout in not just the 2 you mention, but also the 1...d5 line of the Sokolsky, the Reti (are you going to tell me the Sokolsky and Reti are just like the French?)
You have to look at pawn structures. There are 5 main types of pawn structures:
Closed/Blocked - This is where both center files are completely blocked, no central pawn can be moved, and play is on the wings. This occurs mostly in the French, Kings Indian (hint hint), certain lines of the Nimzo-Indian, mostly those where black goes for a dark square blockade with c5 rather than d5 (hint hint) and the Czech Benoni (hint hint)
Open Center - A minimum, one central file is completely open - Petroff, Exchange French, etc.
Static Center - One file is blocked while neighboring files are not blocked, but advancement can cause other weaknesses. Prime example of this is the orthodox QGD or the Carlsbad Structure.
Mobile Center - This is where one side, often White, has the big center and is chipped away from the outside and not blocked. Unlike the Kings indian, which usually leads to the blocked center, you are mostly talking Grunfeld and Alekhine here.
Dynamic Center - These are your amorphous centers that do not fit the other 4, like your Najdorf Sicilians, for example.
Go back to the Closed/Blocked Center. There is where you should be looking. Kings Indian, Nimzo-Indian with a dark-square blockade approach, or Czech Benoni.
In many ways, this makes sense. 1.e4 is a pawn going to a light square. Fight on the light squares, making him advance it, will plug up the position (d4-e5 vs d5-e6). 1.d4 is a pawn to a dark square. Get him to advance it requires a dark square approach, like ...d6 and ...c5 or ...e5. Notice the blocked positions of those like the Classical Kings Indian, Hubner Variation of the Nimzo-Indian, or Czech Benoni. All dark square complexes.
As far as White - toss the London. Biggest problem is that those under 2500 do not truly understand it and iften take the "I will close my eyes for the first dozen moves" approach and often get bad positions. They assume c3 always, never c4. They assume h3 all the time, even in lines where it is weak.
You are better off taking an approach with more diverse positions. If you enjoy the closed game like the French, there are multiple ways to go.
1.d4 - Queens Gambit, Nimzo, Kings Indian, 5.b6 vs Benko, 4 e3 vs Grunfeld, etc.
1.e4 - Slow Italian, Closed Sicilian, Advance French, Advance Caro-Kann
I would highly reconsider your choice of openings if you are a French player. QGD and London are not the answer.
If this means anything, I am also a French player, I play the Nimzo against 1.d4 (and former KID player for a number of years), and white? I do play the Fantasy against the Caro-Kann, not the advance, but I do play the Slow Italian, Closed Sicilian, and both 3.e5 and 3.Nc3 vs the French!
I also sometimes play 1.Nf3 or 1.b4 as White.
Hello, you guys (and girls)!
I'm an intermediate player (rating about 1900, OTB).
Reading some articles, I realize that in my level I have to take one system for White, and one system each against both 1.e4 and 1.d4. So, I'm thinking to take The French Defense against 1.e4 and The QGD against 1.d4 for Black and the London System for White.
Said that, my question is: Are the French Defense and the QGD related openings?
[EDITED] When I say "related", I mean: they are different, but they work well together?
For instance, let's say that my opponent plays 1.c4. So, I'm wondering if I can just play 1...e6 (aiming for ...d5) and eventually I will get the same positions/pawn structure in the French and/or the QGD. Or, if he plays, for example, 1.f4, I can play 1...d5, and later ...e6 and ...c5, and I will get a French look-like opening again.
Am I being in trouble thinking like that?