You'll find quite a few current and former Nikon shooters using Fuji gear here and on our sister site, CamerasWithoutMirrors. I haven't shot the XPro1 or XPro2 personally. I notice that you have the two Fuji pancakes as your kit. They are fun lenses! Enjoy!!
27 is, but to me 45mm just isn't a great all-around FOV like 24mm. That 27 is extremely sharp for a $200 pancake though.
I had the 18mm but never used it once I purchased the 16mm f/1.4. No comparison size wise but magic happens with the 16.
I always forget how light the Df is compared to my old D800E. You'd only be talking about a half of a pound difference at 24mm equivalent with primes.