I always assumed you were best off hitting the clutch (like fully) at the same time to de-engage any passive revs from the engine?

I'm now second guessing myself and wondering if you'd be missing the impact of engine braking which would be more significant? I guess you'd not want to use the clutch when going down a hill because it would probably make things slower, but not sure if the answer on the flat.

We are taught in driving lessons here in the UK to do clutch and brake, but I never thought about what actually stops the car faster. I'd be happy if someone wanted to inform me so I can avoid a long internet rabbit hole about engine braking :).