Rockwool was around forever before fiberglass, very dense. My detached garage/shop has it and it does help a bit versus fiberglass.

You can buy acoustic panels (think music studio) but that is $$$ as well.

My guess is the best bang for the buck would be the extra isolated layer of sheet rock. comparatively Easy enough to slap up versus tearing out everything to get at the insulation which in my experience only can provide minimal effect.