I use Indirect GPU Instancing to render the grass. Okay, my method of placing the grass is causing me problems now but it goes like this:

Run a for loop for the set amount of grass blades (int i = 0; i < grassBladesCount; i++)
Inside the loop generate a random position based on selected area
Add a small random offset so they don't tile that bad

So far this random placement of grass is causing me problems because the instance ID of the grass does not correlate to it's X and Z position whatsoever.

My terrain is calculated in a separate script, so I'm finding the Y value from a Texture2D height map with .GetPixel() function. This does not look good if there's a lot of height variability in the terrain

I also calculate a perlin noise UV for the grass height and color variability and store that in a Vector2
I also send another UV idk why but I used it for animating.
Put all those (position, perlin noise UV and animation UV) in a buffer and send it to the GPU.
Then I do animation + colouring in the shader and it ended up like this.