I have to agree with Domenic_S, it's probably the solid core doors (I'm guess the jambs and sill are well-sealed also) that's providing most of the benefit more

I have to agree with Domenic_S, it's probably the solid core doors (I'm guess the jambs and sill are well-sealed also) that's providing most of the benefit moreso than the rockwool. Staggered studs are an option, resilient channel also works well, provided that it's installed correctly.