I am looking to fashion a passably believable fantasy ship for a crew of about 30 privateers* (see remark, this could be changed if needed, although I prefer not to have a massive crew in the story). I imagine this being something like a two-masted ship to the general tune of our traditional pirate ships, but with a team of oarsmen (I'm thinking 12) acting as an auxiliary to the sails for increased speed. I also imagine the ship would have its upper forecastle and poop decks, the main upper deck (with galley and officers' quarters), a first-level internal deck with crew hammocks and oarsmen ranks, and a lower orlop/hold primarily for cargo (and possibly a small brig).
For weaponry, I intend to make use of devices such as grapples, ballistae, flaming arrows, and large crossbows mounted around the ship...plus some magical-type stuff, of course. They don't use gunpowder in this world (at least not at this point in history). Anything technological tends to come from the use of special gems and power crystals. Small automobile-like vehicles are in limited use, but nothing large-scale enough to propel a ship at sea.
As I describe this, does it sound plausible? What might I be missing?
What types of ship might this resemble - galley, schooner, xebec, galleon, carrack, brigantine, some hybrid thereof...?
Approximately how fast could we expect this ship to move in generally favorable conditions, with and without the use of the oars?
<sup*this crew takes jobs for hire to bring in high-value goods and goods that might require somewhat roguish tactics to obtain. For example, they might go to another nation to retrieve a rare artifact held under guard. Or, they might bring in a high-value shipment that requires special protection and defensive measures. I figured "privateer" might be the best way to brand them...but if you suggest something better I'm happy to hear it