Snakes at 30 yards? I'll bite my tongue on that one.

If you really want it for snakes, a 10" pistol barrel is plenty long. If you want it as a shotgun for game for the cook pot the 21" or 23" is the ticket.
The .410 barrels from the Classic Contender frame days will work on the G2, so that gives you the barrel length options you want with factory barrels instead of having to buy custom.
The 21" VR barrels are smooth bore with a removeable full choke.
The Super 16" VR barrels are 45/410, so do have rifling and a removeable full choke just like the 10" VR and 10" bull.
I've had several over the years (10" VR 45/410, 10" Bull 45/410 and 21" VR). Only ones I liked and found to be really useable though as shotguns beyond PBR was the 21" smooth bores.
YMMV