You say you want to shoot wide. How important is that to you? You will be able to go widest via a full frame sensor. The question mainly comes down to if you want full frame, or if you want compactness.
If compactness is what you want best, then go mirrorless, but only if you are fine with staying in the realm of crop sensor territory. I could explain why, but this article does it just fine:
http://petapixel.com/2016/04/04/sonys-full-frame-pro-mirrorless-fatal-mistake/
And, if you do go mirrorless, get the Fuji. I'm hearing good things about the XT2, but the XT1 is still an awesome camera. I have friends still using it, and they take great pics.
If you want to shoot wide, then full frame is your best bet. I dunno if I'd go with the 24-120 f4, though. If it were me, I'd probably stick with prime lenses for wide landscapes. Something like the 20mm f1.8, or the 35mm f2.
I shoot with a D800E most of the time, and for landscapes I use the Rokinon 14mm prime lens, the Rokinon 24mm tilt shift, the Nikon 50mm f1.8D, or the Nikon 85mm f1.4D. I care about quality and dynamic range the most, so it's Nikon full frame for me.