Also, if memory serves, the torpedo launchers aboard the Defiant, at least the ones depicted in the the TM, were no where near 20-40 meters long and they were firing Quantums.
OTOH, the TM and the onscreen MSDs did portray those launchers as having the generic shape familiar from TNG - the long main barrel accompanied by another, parallel one to create the visual resemblance to today's guns with the prominent recoil absorbers, plus a loader doodad atop.
This might indeed be but one way to put together a torpedo launcher, but a favored way for starships nevertheless. Some of the launchers of DS9 might be simple revolver magazines without any real barrel attached, firing "peppermill" style, while others might have all sorts of fancy arrangements we cannot even imagine but which necessitate the funny box shape witnessed on those docking pylon weapon stations. And some of the "secondary" launchers on the E-E, apparently incapable of having long barrels, might be "point defense" torpedo turrets as well.
I say the more diversity, the better. It's sort of sad that the mighty starships have the thrilling specifications of being armed with "phasers" and "torpedoes" and... Well, that's it. And worse still, that's all it can
be. Inserting at least some hint of variety, such as "Type 8 phasers" or "Mk III microtorpedoes", puts the thrill back in the technobabble.