Some production environment concepts for GALAHAD 3093. The sweet spot between speed and detail is often simple block out geometry with line art sketching over the top. A good art bible can let you get away with looser sketches as well.
The relationship between concept and model has to be tailored to circumstances. Large areas of hard surface geo are almost invariably tiling textures and decals, so suggestions of breakup and details point the modeler at 'what you have that fits best'. Mutual trust is integral.
Some concepts can be very polished, but most are not. A way to think about concept art vs. illustration is functional: Concept art is embedded in a larger process and is not typically the final product. There are gray areas, particularly during preproduction or making pitches.