With the right loads, a .58/24 gauge smoothbore should be adequate for most hunting--the only reason I went to a larger bore was that I kept running into bears. But to use the 24 gauge effectively, you may have to change how you hunt, and there may be conflicts with local laws (like minimum bore sizes or requirements for the use of buckshot). Bow hunters seem to do well with one, which sort of fits with the historical market for tradeguns. Getting close can be key.
For example, the 24 gauge tends to not work out well pass-shooting waterfowl. If you have the option of switching to puddle-jumping so shots tend to be closer, it can work fine. It isn't my first choice for quail hunting, but the little Ketland double I had worked ok when jumping a covey, and great when following up single birds once the covey broke.
IIRC, my shot load was 70-80 grains FFg/equal volume shot. For upland hunting I mostly used #7 1/2 or #6 shot, #4 for turkeys and puddle-jumping ducks and geese. Those loads gave me decent patterns to 30 yards, and I could actually find the shot locally. Shooting larger shot left holes in the pattern; #5 patterned beautifully, but at the time, my only source for #5s was salvaging the shot from loaded shells.
With ball, I mostly stuck with 80gr FFg and a patched ball. At the ranges I hunted, this load would shoot through a mule deer (or elk at the right angle) and had enough power to take the one moose I shot with it. None of my shots with ball at large game were taken past roughly 25 yards.
