There are multiple branches of the troopers in Alaska, such as the blue shirts (normal), brown shirts (wildlife), investigative (undercover agents), and SERT(special emergency response team, kind of like elite SWAT). Depending on your position I guess you would choose from there. The brown shirts most likely carry the 20 because of where they operate.
I've heard of Alaska troopers carrying the 10mm to defined against the mighty grizzly. I've never looked into if that's true or not. Maybe someone here knows.
Not sure about that, but in my exp if they are stepping into the woods for over 50 ft they don’t go without a 12g with slugs. I have had a lot of time in the wilds of AK on remote wildfire and it’s not uncommon to order up a shotgun from the warehouse