If I remember correctly, the Flexbody will give you rise, but no fall,
I think there is rise and fall, but no sideways shift at the same time... unless you put the Flexbody on its side and then the rise or fall turns into a side shift only.
There is some bellows extension, but you probably wont want that for landscape anyhow.
As far as the Phase digital back, Shutay is correct in saying you will need to buy a wake-up cable, but if you are using a Leaf back such as an Aptus 22 (sort of an equivalent to a Phase P25) you wont need this cable as the back is "always on".
But you will still need to compose your shot on the ground glass first - and then put the back on which will expose it more to dust, or shoot an image and check it on the backs display... (not always the best and fastest way to confirm sharpness)
I dont know how MF will be quicker for you than a D3x... Still... it is a nice little camera that I enjoyed having briefly.