Without multi quoting and filling my reply with endless words...
I stated that carbon build up alters the note, not drone. Droning is a manufacturing issue, if a system drones on a car it's either not a quality system or it's not the right one for the car IE twin 3" with no resonators on a V6.
The characteristics of the exhaust will affect drone rather than size. People can also confuse drone for noise, if a system is too loud it can be incorrectly labelled as droning when it's actually not, it's just loud. A 3" will be louder than 2 1/2" of the same design. Droning is caused by the existence of certain frequencies that the ear doesn't like, these are built in to the system because a) the builder has no idea, b) the builder is working to a budget or c) the wrong components are put together (see a).
It depends on manufacturer regarding glass packing. Some mufflers don't have it and rely on internal baffles and tubing to reduce noise, I was referring to sports/performance systems, most, if not all, have glass packing to absorb frequencies that harm baby dolphins so that they can retain flow and reduce noise without being restrictive. Some are successful, some not so much.
Regarding the bugle, if you were to have the same person play the same series of notes on the same bugle clean and then with a layer of carbon internally then absolutely it will sound different. That was my point. It alters the tone, not the drone.
If you have ever heard a flat plane V8 or a set of cross over headers then you will know why the V8 sounds like it does. It's the difference between say a HQ 308 and an F1 race car. Cross plane V8's fire 2 cylinders on the same bank in each full cycle (LRLLRLRR) where flat planes fire alternatively (LRLRLRLR).