So who hog hunts with a shotgun and how well does it do? What is your setup?

Only challenge with a shotgun is your distance limitation vs a rifle. I shot two in one sounder with my VersaMax shooting a slug as the first round and buck shot for the next three. I was about 25 yds away in a popup.

Get close enough and a shotgun will put the real hurt on one.

What choke is appropriate for buck? I tried some out of my turkey gun this weekend and xtra full blew the pattern open. Using 20ga #3 buck.

I shot a javy with a shotgun once.
#8 shot, modified choke.
While quail hunting our pointer was attacked by a javy and I went to try and stop the the dog from getting maimed.
The javy turned on me, I got him square it the head from 6ft.
The dog had been punctured and sliced up pretty good. After some amazing in the field first aide, the dog was fine.

Rifled barrel. Sabot slug. Good out to past 100 yards. Drops em deader than easy credit.

I've never hunted with one, but there's no reason a decent slug launcher with rifle sights won't work within a hundred yards.

I hunted deer with a shotgun and buckshot for more than 30 years. The general rule of thumb is to use an open choke for the tightest patterns. However, My personal experience is that every gun shoots buckshot differently.
Test your shotgun with a variety of loads and stick with the one that produces the tightest pattern at 30 yds.
With a 20 gauge your somewhat limited in variety, but different manufacturers of the same buck shot size can pattern very differently.

I have an old bolt action 12 gauge goose gun that I have used for deer hunting up north and I might take it out to use on some hogs this winter. I believe it has an IC choked barrel so that's the reason why I shot rifled slugs out of it years ago. I also used a Mossberg 695 bolt action slug gun for years and that thing kicked like a mule. Both would knock a hog down easily. I used Brenneke KO rifled slugs and would get good groupings at 100 yards with them. Up north using a shotgun or a muzzleloader were the only firearms allowed for deer hunting.

Extra full is too tight of a choke. Use a more open choke for large buckshot. Also try flight control wads or versitite (sp) wads to help with patterning.

We use KelTec KSG's when the corn gets tall, as it makes good clean rifle shots outta the chopper almost impossible. 2 3/4" 00Buck at about 20-30 feet does the trick. 88 plus took dirt naps this day in the video attached... This year all of our KSG's will be suppressed.
https://youtu.be/o1HT1bQfMKI