Brand of ammo, chokes, shot size, etc. highly dependent upon what a particular gun "likes" for best pattern. And the best way to know for sure is to buy at least a 5-pack of each and try on patterning boards/targets.
If I were to attempt such with a 20 gauge, the relatively new Remington Hevi-Shot would be a first choice. And some "Shoot 'N See" turkey head targets. Just guessing probably good out to about 35 yards, maybe 40. And surprisingly, sometimes - with a modified choke.