To answer a few questions or take a guess as the case may be.

Yes it comes with 2 3/4" chambers. But this is no handicap. I checked out the available 20ga sabot slugs from Federal, Remmington and Winchester. The fastest of all was a 3" Winchester offering at 2000fps. Next fastest is 1900fps and Federal makes these only in 3" but both Remington and Winchester offer these in 2 3/4". The Winchester offering is the Nosler Partion Gold 260gr sabot slug and the Remington the Ultra Coreloct bonded core slug, I think 260grs but could be mistaken. FYI, the ballistic table that Winchester displayed for the 1900fps 2 3/4" Partition Gold showed .7" high at 50, .8" high at 75, zero at 100 and -1.7" at 125yds. WOW!

The regulation device is sure to be at least somewhat similar to others, like Merkel's small and medium rifles ar equiped with, and likely to either bring together or spread the muzzles. From the photos it looks like it works with a screw divice parrallel to the bores, in between the muzzles.

I'd be willing to bet that the rifle barrels will pattern like hell. But I could be wrong. I'd also bet that a second set of barrls could be ordered for shooting shotshells.
I thought about that but decided against it because I wanted the gun to closely resemle my bug bore double, and if it had shot barrels, it would have begged for a straight grip instead of the pistol grip. I doubt that shooting shotshells in it would be harmful to anything other than your patterns.

As for why it cost less, I'll venture that pressure has something to do with it, plus its machine made for the most part and from mostly existing parts used on their 20ga RBL's, doesn't appear to have labor extensive rust bluing, little engraving and only adequate wood.

Either way, I'm looking forward to getting mine and getting it set up and shooting right well before our shotgun only deer season!

JPK