If you can obtain a rifled choke you can shoot saboted slugs with far greater accuracy and longer range, but that's not necessary at usual defense ranges. if shooting rifled slugs from a smoothbore, a cylinder choke is best, skeet second best, improved third since that's the progression towards tighter choke.
As to point of aim with slugs from a smoothbore, standard shotguns have a slightly high "line of fire" because a game bird will normally be rising. But it's not of great consequence at usual defensive ranges.
If you expect engagement at distance and HAVE to rely on a shotgun, a rifled choke and sights would be advised. But, would be better to switch to an AR or other rifle, i.e. use the right tool for the job....