Yeah, it mostly is just sound. There's no special particular sound that defines the genre, as it is a reflection of all genres.
But if you had to define a starting point, and this is due to a number of factors, I would say you start with a clean-ish amp of the Vox persuasion. And you build gain stages based on boosts and ODs. Sometimes multiple amps are a thing, whether for stereo or blending. There may be more or less delay and reverb than in some styles. There may be more or less gain. But the gain is almost always pedal based.