Just north of you... a bit of a 'rain expert' you might say and this is a good question. But rest assured, not an issue for the reasons shared already.
In fact, a posi rear might hook up well but when they do break traction, you can go for a bit of a ride. They can also 'push' the front end through corners like a half track...depending on the posi and how easy or hard they 'break' for a turn.
Light to medium rain, 2wd is fine. Dry and on the gas really hard - really composed and no '1 tire fire '(I like that).
Heavy rain or medium rain and steep hills, I use 4A. Light to medium snow, 4A. Really slippery, steep, or challenging snow 4WD.
You can turn the nannies off like traction and stability control or leave them on. The drive modes change them too. All pretty well thought out actually.
Slippery mode - unless you have a lot of black or glare ice or some super slippery silty mud, I hate it. If I was going to get someone to drive my truck who was a bad driver, slippery would be good...it really mutes the inputs. I find it is more of a liability than anything, but have used it on ice.
There is a locker for the rear. I haven't used it on the road except in deep snow. Off road it can be really helpful but most of the time for most of the offroad it isn't needed. When you do need it, it is a game changer.
I have the torsen front diff and so far, again, really happy with it.
If you are in the SCREW, then the weight distribution front to rear is like 53/47% or something. Not quite 5050 without a load in the back, but not like pickups of old with a big block and 8' bed. It makes it really planted. I have a rack and tonneau and that adds about 150 lbs static which is a benefit, but not necessary.