What's the perceived wisdom on changing the various transmission/diff oils, frequency etc. Thanks in advance.

hey! For differentials, especially rear differentials, oil changes are often done every 80,000–120,000 km. 

Powershift (I know!) sensibly advocate changes 3yrs, 30k miles which can't be missed unless you have a transmission death wish 

My sense of "perceived wisdom" on here is that Sealed For Life means lifetime of the Ford warranty (after that, they don't care) NOT your expectations (mine is 20 years+!)

Therefore if there's a recognised procedure, drain and fill plugs and oil of correct spec, filter etc (regardless of cost) if you are keeping it and want it to last, Just Do It!

The slip modifiers in the transmission fluid break down, all auto gearboxes require servicing, some more than others. My partners' 2018 Edge has the later powershift auto, I would say that it may need a fresh adaption of the clutch motors. They need to come in a little faster when coming to a stop, releasing of the clutch when pulling away feels just right. The gear change is quick and smooth, no jerking at all. The adaption is something I'll look into at a later date.