Rifled slugs are meant to shot out of only a smooth barrel. They have the "rifling" cast into the slug to cause it to spin in the barrel and going through the air. This rarely matches rifing in the barrel if you have a rifled barrel and can make them pattern goofy. Sometimes it works out but usually it is less than ideal. Max range IMO is 100-150yds out of a smooth barrel.
Sabots (at $10+ per 5) are meant for a rifled barrel. There is nothing to spin them in a smooth barrel... basically you have a musket. 150-200yds is what people consider their max range in a rifled barrel.
There are some slugs that are marketed as working in both smooth and rifled barrels, my smoothbore likes Breneke KO slugs about as well as my brothers rifled barrel does.
Shooting a slug through a choke makes me cringe. I have heard others do it, you have the intial bang as the gun goes off then a weird thump when the choke farts the slug out. I don't know what they had for chokes but I didn't like it.