I frankly like guns and think the lack of them in most "fantasy" settings is kind of annoying;
I wouldn't want anything automatic;
fire lances, rocket arrows, hande-gonnes; matchlocks, wheel-locks, flintlocks; heck even cap and ball or cartridge firearms if you have the kind of supply chain that can get you mercury sulfate and the kind of production line to produce copper or brass firing caps; though perhaps those should require some additional checks and conditions;
each stage requiring a combination of "infrastructure" (even if it's not 'your' infrastructure, there's someone who has to either find a guano cave, nitrate deposit, or fermenting animal waste, then mix and mill it into gunpowder, find and refine lead, etc.)..
the major advantage should be to cannons and their ability to take down thin stone walls;