This is one of the most over treated areas on a car. The first time I treated a trunk lid, I used so many layers of vibration damper that the lift springs wouldn't hold the it up any more. The trunk lid is not usually a huge entry point for noise. It can be an issue for resonance and definitely rattles.
It is often over-treated by people going after rattles indirectly. Sometimes a sub-woofer in the trunk is creating enough changes in pressure to displace or distort the trunk lid. Somebody somewhere decided that steel is best reinforced with aluminum foil.
If your trunk lid doesn't have a trim panel, you will see any treatments you add. Some people care, some don’t. A few CLD Tiles and some silicone isn't going to be a problem but overloading a trunk lid can overwhelm the shocks or springs. Good idea to see if your trunk lid will stay up after treatment before actually applying the materials. I'll never admit how I learned that.
I get as much CLD Tile™ on the outer skin as I can, up to 25% coverage or so. The red dots are RTV silicone. This installation was part of a stereo installation and I was concerned that the inner skeleton might rattle against the outer skin. Simplest and completely effective solution is to add a few dabs of RTV Silicon.
Again, not a huge problem for noise. Might be worth adding a barrier if keeping sound inside the car from being heard outside is a top priority or if the lid wraps down to the bumper and there is a lot of noise coming out if the tailpipe.
Hatch Doors / Tailgates
Again you want to test the lift mechanism before applying anything to be sure it won't be closing on your head after treatment. CLD Tiles™ and 3/4" Hydrophobic Melamine Foam or CCF are almost always safe. MLV can be a problem.
Square inches divided by 240 for CLD Tiles™. Possibly 1 or 2 extra for the trim panel?
Square inches divided by 144 for CCF, MLV or 3/4" Hydrophobic Melamine Foam.
Don't forget a few Velcro Strips if you will be hanging CCF and MLV.