What are some ideas for black in the Ruy Lopez when white plays an early d3?

Question

If white plays an early d3 in the Ruy Lopez (presumably after c3 to give the light-squared bishop a retreat square) what are some ideas for black? I'm talking about those lines where white doesn't push d4, at least not immediately, but plays more calmly with d3. Svidler made a video series about the d3 Spanish on Chess24, but it's a little hard to tease out the ideas from the moves. I'm looking for an answer here that articulates in plain words what plans and ideas black has at his/her disposal when playing the Ruy Lopez against an early d3.

I've outlined, below, some plans and ideas with which I am familiar. But some of them may be faulty. This is just my modest knowledge of an opening (d3 Spanish) with which I am not that familiar.

1. Playing d5 and often then d4. This can be followed up by dxc3 bxc3 b4 to undermine the pawn on c3 and free up the d4 square for occupation (perhaps by a knight).
2. Rerouting the f6 knight to d7. This gives black the possibility of f5, which could be viable depending on the situation. It also allows the dark-squared bishop to go to f6, where it pressures d4 and might eventually end up on g7. The knight on d7 can then go to b6.
3. Playing on the kingside, Kings Indian style, by maneuvering the f6 knight to g7, playing f5, perhaps rerouting the c6 knight to f7. Why often responds to this plan with an early g4, discouraging black from playing f5, and playing on the kingside him or herself.
4. Playing on the queenside, starting with the moves Na5 Bc2 c5. A rook can go on c8, and then black can push c4 or b4, and try to open up the queenside. However, it can sometimes be difficult to pry open the queenside without an open c-file, as you often get in other lines.

Plans 3 and 4 are general plans that apply to most Spanish openings, whereas 1 and 2 are more typical in the d3 Spanish. I guess I have a passing knowledge of what to do in this opening, but, I still feel like it's not nearly enough.

Are there any key ideas or characteristics that I am missing, that are specific to the d3 Spanish? How is it strategically different from other Spanish openings? Are any of my above plans faulty? Can any of the above plans be elaborated more?

[fen ""]
1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. d3

Answer 1

I have found some ideas for you from an online source. I hope that this helps you!

Quote: “All this being said, there is some downside to playing d3 one move earlier -- there always is. Seeing as the idea of playing 6.d3 following 5...Be7 is to have black commit to developing their bishop to that square, playing d3 a move earlier with 5.d3 allows black to play differently and more advantageously. This is done by black playing d6 (protecting the e5 pawn) followed by g6 and Bg7, which is a useful and common maneuver found in many Ruy Lopez lines. Black here is able to develop their bishop to g7 immediately, and white can't punish this with an early break in the center with d4 (a la the Fianchetto/Smyslov Variation of the Ruy Lopez with 3...g6), as it comes with a loss of tempo (time) because the d3 pawn has already moved. Therefore, black is thought to equalize rather easily if they conduct this early Bg7 maneuver against 5.d3 (occurring roughly 20% of the time according to databases), as black essentially reaches a Deferred Steinitz or Russian Defense type of position with an extra tempo. You can think of 5.0-0 as a very useful waiting move in relation to the 6.d3 variation, in that it waits for black to commit their bishop so that white may potentially hang on to an advantage somewhat longer.” -Source: https://hubpages.com/games-hobbies/Chess-Openings-The-Ruy-Lopez-with-6-d3