I'm also not good at graphic, only speaking from experience which isn't unique to myself and some logic tied to it so they hold some merit i would hope. Until someone proves me wrong that is. And i try to add 'not sure' or something similar when i'm about to say something i am, well, not sure of
LFS does not use pixel shader technology so the texture mapping doesn't play a role in loading time because it doesn't exist. Would it play a role should it exist? Yes but not by very much. It's not as large in size as a texture but it's more of an information calculated on the fly, every frame, then added to texture surface information, resulting in change of its appearance. Such as rainy roads, shiny metal surfaces in bright light conditions, adding visual appearance of bumpy surface on an perfectly flat texture, stuff like that. When done with care it makes a more immersive environment. It's down size is very heavy GPU load. Not in loading time but pure processing power. It is still more efficient then adding more polygons to achieve the same level of visual detail.
In LFS the roads are simple flat polygons except on places where two polygons join at different angles. But, if you look the suspension forces while driving on a visually flat surface like Blackwood back straight it appears you're constantly driving over bumps. But they aren't there, so what are they? My theory from when i first saw that is that those bumps are programed into track elevation info or something. Kinda like the shader stuff but it results not in visual appearance but a virtual physical force, affecting handling. Way to save on GPU power and is pretty neat how it's done.
Those different colored copies of the images i don't think are textures as we know but information how to stick shaders to it. If that shader info was 4x larger as indicated on your picture the texture loading part would take 4x times longer, but from my experience that isn't the case. My experience shows negligible difference in loading times without using shaders compared to slight increase of using it (different game ofc).
Different sizes of them are what you have said - LOD textures that are used at far distances. Commonly used is open game areas to save on memory so that environment closer to you can be presented in more detail. And lower resolution textures also look better at far distances because the high detail of high res textures would be lost on the relatively big sized pixels on the LCD monitor making it look like blurry, jittery (when moving) mess.
Nice example of that are the high resolution road textures for LFS. The detail is so high that it is smaller then the pixels are able to present and it ends up looking like one shade of gray from anywhere above 10m distance and/or lower view angles. Depends on monitor resolution but not by much.
Those generating and rebuilding can mean anything, only the author knows for sure
My guess is they are expressions for various stages of texture loading and placing them in 3D space. Nothing too fancy.