The "standard" and "conventional" insulation for fiberglass boast in our size range is vinyl / foam composite insulation. Most of the suppliers to this industry manufacture a very similar laminate:
A vapor barrier face
An absorption layer
A vinyl noise barrier
And a decoupler layer
Overall thickness varies from 1/2" to over 2", typical barrier weights are 1 or 2 lbs per sq ft, the simple rule of thumb is "more is better."
What stops noise is mass. If it isn't heavy, it's not going to do much.
There are also some excellent acoustic carpet underlayments and noise barriers for use under vinyl or hard floors.
Both real engine room insulation on bulkheads and overheads and a treatment under the finish floor will be the Best in a Good-Better-Best contest.