If you want to do it right, you want a combination of sound/vibration dampening, sound blocking and sound absorption. Good explainer here.
https://www.secondskinaudio.com/sound-deadening/car-soundproofing/
I used their Luxury Liner Pro. Not light, but it works very well. Curves take some effort to make seamless by trimming the mvl edges. It's about the same thickness as the horsehair and tar that was in my car originally. Maybe a little thicker.
Do not make the common mistake of covering huge areas with 100% sound dampener (like Dynomat or Damplifier Pro). You only need to do larger flat areas that can vibrate, and 25%-60% coverage is plenty. People cover their entire interior with this stuff, and it just adds unnecessary weight.