Same as I did ever since War Mode was introduced: off. It also no longer makes sense with the story since the Fourth War ended about six years ago in-universe.
Story wise there will always be old hatreds and small skirmishes behind the scenes. Kind of like classic wow where there wasn’t a full blown war between the factions, but stuff still occurred behind the scenes that maybe the factions didn’t condone.
I find it hard for 100% of everyone to just forgive major events that the other faction did to cause the death of their peoples. Just like in real life how there are real world prejudices that can never truly go away.
Always off 
Always off. I’ve never understood the appeal of allowing some random person to interrupt your gaming.
I won’t play with WM on because getting killed by other players sours my experience.
I am all for players questing with WM on… it means less people competing for mobs while questing in PVE.
Sure.
I might attempt a naked character run with wm on and just grind mobs for 10 levels