You will need to try various slugs to find those which your gun prefers. I have not found 3" shells to shoot any better than 2 3/4" but part of that is the way I experiment finding a load-start with the least expensive load I can readily find and work up. When I find something that keeps 5 rounds in a palm sized group I stop. The price generally precludes 3" shells but I don't miss the added recoil.
The closest I can suggest for a "one stop sabot" is the Remington Accu-tip. It seems to group at least adequately in most slug guns. It is my first choice when I don't have time to experiment with slugs. At $3+ per round it is not my first choice.
In theory the 3" shell will provide a better gas seal in a 3" chamber, but that is splitting hairs. Slug guns are getting more and more and more accurate, but they are still not sniper rifles.
The lion and tiger might be stronger, but the wolf does not perform in the circus.
Years ago I was told that stuff about 3" shells in 3"chambers for the fully rifled 12 ga. 870 I use in shotgun zones. Found out by experience that it wasn't true; at least not in my gun. I run 2 & 3/4" Sabots because my barrel is more accurate with them. Not only that but I also discovered that deer can't tell the difference which slug I hit them with. So I just go with accuracy.