Hey there @jmiller1314,
the difference in numbers of cannons on the Galleon (in relation to it's crew size) compared to the numbers of cannons on the Brigantine and Sloop most likely stems from changes that were made during the development cycle of the game.
If you take a look at the Sea of Thieves E3 Announce Trailer from 2015 you'll notice that the size of the Galleon crew was at one point 5 players instead of 4.
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![alt text]()
That number was most likely reduced for balancing reasons and from the data the team gathered regarding crew dynamics and such.
What didn't change was the existing aesthetics of the Galleon.
That's why the Galleon still has 8 cannons with only 4 crew members while the later developed Sloop and Brigantine had their numbers already adjusted to their respective crew sizes.
Stuff changes during development, that's all there is to it.