I like having the ability to use the E-Locker in my truck in 2WD and 4WD........nice feature, some only can lock in 4WD
I do believe the Ford E-lockers can be used in 4WD.
And BTW, as the OP I am overwhelmed with all this info. Five years ago when I bought my 2500 RAM I just wanted it "4 WD" and that's it. I didn't even know the Ram would come with limited slip. (It did.) And if I go with the new 2018 Ram I'm taking away to stay with the factory rear limited slip and then add a locker on the front IF I need it. But if I go with the 2018 Ford to go with the E-locker option. (Ford does not have a limited slip option on the F-350 SRW chassis cabs.)
It sounds like either option will be better than what I have now and I've never been stuck in five years including five days on the white Rim Trail last week! So maybe it comes down to the perennial Ford vs. Dodge debate including is the 6.2 Ford gas with the Selectshift tranny or the 6.4 Ram Hemi with the Aisin tranny better? Guess this one deserves its own thread though!