How can I lower my program size if all of my assets are one chanell?

All of the assets in my game are white gradients. Essentially they could easily be stored inside of an alpha channel only texture.

How can I use this to speed up rendering/texturing and the size of my program?

Lower Size:
I know of programs that can find the optimal format for an image maybe lowering its channels somehow. Is this the only way?

Texturing Faster:
Would texture2D calls be faster if I just put texture2D(coolTex, uv).x? Or would that be ultimately slower or cause code branching of some sort?

I didn’t test it, but I would guess that the easiest way is to just create a texture with a 8-bit format.

One of those: GL_R8UI, GL_R8I, GL_R8, GL_R8_SNORM

Alpha-channel textures are deprecated in modern OpenGL. Use a GL_RED texture instead.

You can obtain behaviour equivalent to a legacy GL_LUMINANCE texture by using glTexParameter() with GL_TEXTURE_SWIZZLE_* so that green and blue are both taken from the red channel. This may be useful if you need to use such textures with a shader which is expecting RGB. But it’s better if you can write the shader to use a single float rather than a vec3 whose components will always be identical.

Reading one component from a three-component texture won’t be any faster than reading all three components. Using a single-component texture will be faster as it will reduce the memory bandwidth. Subsequent processing may be faster if you’re using a single float rather than a vec3.