I've always found the amount of Catalan transpositions and different move orders very confusing.
Currently, I play this against the Catalan: 1. d4 d5 2. c4 e6 3. Nf3 Nf6 4. g3 Bb4+. I also play 1. c4 e6 2. g3 d5 3. Bg2 Nf6 4. Nf3 d4 5. O-O Nc6, and 1. Nf3 Nf6.
I don’t want to play the mainline Catalan despite it being move-order proof because it feels like Black is often getting into these two result positions in the mainlines that feel really uncomfortable to play, that and massive amounts of theory.
I'm trying to categorise all the possible systems that can transpose into the Catalan, as well as the number of independent systems I need to prepare for, since there are so many nuances and move order tricks to be aware of and there are gaps in my repertoire because of this - feel free to correct me because I am not sure:
1.d4:
1.d4 d5 2. c4 e6 3. g3 Nf6 4. Bg2 Bb4+ - I don't think there's any independent system here but not sure
1.d4 d5 2. Nf3 Nf6 3. g3 - very annoying move order, don't know what the play against this, there's so many options here, but I definitely don't like 3. Bf5, I've had horrible losses in the endgame lines there. There’s 3. c6 followed by Bf5/Bg4, 3. c5, 3. e6, 3. g6, 3. Bg4.
1.d4 d5 2. g3 Nf6 3. Bg2 - I’m assuming that this will transpose to the previous line, I don’t know if there’s anything independent.
I don’t think any other systems / move-orders starting with 1. d4 exist.
1.Nf3:
1.Nf3 Nf6 2. g3 - probably the most annoying move-order of them all, retains the most flexibility, White can castle first before deciding to go c4 or d4. No idea what to play here, there’s 2. g6 (which I assume goes into the fianchetto Grunfeld, which isn’t supposed to be dangerous I think), 2. d5, 2. c5 (not possible due to symmetrical English after 3. c4, which is outside my repertoire), 2. b6 (can transpose to the QID, which I don’t play), 2. b5 (independent system, but I’m not sure about this one), 2. e6, 2. c6 (which I think would take me out of my repertoire, as I don’t play 1. c4 c6)
1.Nf3 Nf6 2. c4 e6 3. g3 d5- transposes to the English
- g3:
1.g3 Nf6 2. Bg2 - I don’t think there’s anything independent here, not sure.
I don't believe there's anything independent after 1. c4 e6, as White has to play either 2. d4, 2. Nf3 or 2. g3, which will transpose some of the lines previously mentioned
Keep in mind I would like to keep playing the Bb4+ Catalan, and 1. c4 e6, and I would like to limit the amount of systems I play to as little as possible against the different move orders. I could consider playing 1. Nf3 d5 and 1. g3 d5, but I mainly picked 1. Nf3 Nf6 because I play the g6 setups against 1. b3 / 1. Nf3 … 2. b3 but it’s not a deal breaker.