Are adjectives just simplified parts?

In the format where a context can have a 'modifier' and can also have a 'part', the ambiguity is strongest when the 'part' has just one modifier; or when the original whole has only one part and its modifiers are more simply handled as as modifiers of the original whole.
For example you can talk about the max speed of a car as a simple modifier of 'car' or you can make it one of the modifiers of the 'performance characteristics' - part of the car. If you were going to talk about acceleration and other performance characteristics it would be better to have the max speed not be a simple modifier of 'car'.