Don't remember which one was installed when I picked mine up, but the chokes are labeled on the outside ring below the threads.
Sabot slugs are for rifled barrels and not recommended for smooth bore. You'll want to look for rifled slugs, which depending on the type have rifling or grooves cut into the slug itself. If you're going to run 3-gun with both slugs and shot, the improved cylinder will likely be your best bet. It's a good middle ground choke that will handle slugs well and should give you the best accuracy with shot...