Cabinet construction is a really complicated subject. You're dealing with a lot of things and there is very little research in the public domain about what works, and a lot of people applying 'static thinking' to paraphrase a turntable engineer on ASR to vibration problems. It's hard to measure cabinet vibration and it's even harder to accurately characterize what resonances are audible.
The stuffing/damping will absorb some of the sound on the inside of the speaker, and this isn't a bad thing, but there are limits to how effective this is, and adding more stuffing to a box can change other box characteristics in extreme cases, and in any case won't be as good as using a different box shape. The best damping of a backwave is a long tube filled with stuffing - see the B&W nautilus design or the Linkwitz Pluto. The problem with these tubes is that you get no bass, so if you want a bass reflex enclosure with some backwave attenuation you accept that compromise. A good argument for a dedicated midrange driver, certainly.
'Cabinet resonances' normally refers to flexing of the cabinet itself, which can re-radiate sound into the room in ways which are undesirable. Stuffing does nothing to stop this. The traditional method to fix this is to make the cabinets more rigid and more massive, but this is not always a good approach, and the consensus now at least among DIYers and other crazies is that some kind of lossy bracing is probably the best approach, where the braces connecting opposite walls of the cabinet have some sort of elastomeric component which turns those vibrations into heat as the cabinet flexes. There are some other approaches but the idea is the same, rather than simply making the cabinet more rigid, which simply raises the frequency at which it resonates, you actually try to convert the mechanical flexing into frictional losses.
In any speaker under say, 5k USD, you're just looking for a heavy and rigid cabinet. Lossy bracing is used to somewhat limited effect in some other speakers such as the KEF LS50.
Speaker modding in my opinion is rarely worthwhile; the best results in most cases come from redesigning crossovers which is a whole other kettle of fish.