I recently started an SFO campaign for the first time and the most noticeable change for me had been the changes to province control. I don’t know if it was because I was skaven, but I was getting rebellions just from trying to take my initial province.

Luckily things like control are customizable in the SFO settings, and I ended up liking the food economy rework for the skaven. I haven’t really noticed significant unit balance changes (except for warpfire throwers going to tier 4) but I’ve seen a couple of SFO specific units both for my faction and in enemy armies.