My thinnest bodied guitar produces the most low end of my guitars, and it's a 35mm thick superstrat, same thickness as an SG. The second most low end is from an slightly thinner guitar thats also slightly smaller. Explorers are 41mm thick. ~15% thicker, not 100%. Thick (and therefore pure mass) matters, but less than shape, imo, especially when the difference is so small. It's about the guitars resonant modes. There are a shiteload between the bridge and nut that dominate, but the modes the body shape allows must be in the tone to some extent, and those the body shape denies must be diminished to some extent. Pointy appendages on guitars take on high mid modes, wide slabs and round shapes, low modes. Explorers have both a wide chunk of wood taking on low modes and pointier elements taking on high modes. Anecdotally, explorers are noted for low end and high mid cut. Vs are all pointier appendages, in a shape that denies the body any single mode that crosses its whole width, and SGs are mostly round slab, albeit small one with a quite freely vibrating neck.
The wood quality probably matters as much, but as more of a filter: if the guitar shape is trying to produce frequencies the wood is absorbing, you don't hear them. Pretty sure this affects high end first. Similar story with sloppy set necks with too much glue (gibson standard MO - they're less likely to make a good join than bad one in my experience). This obviously muddies things, sonically and in discerning whats affecting what in the sound.
