I think you’ll have to! The single biggest change imho is sectors probably.
However, one other change that hasn’t gotten much attention is that independent cities don’t exist.
In AoW3 you might start with a very large Dwarf city near you, or find one early, which might change your game strategy immediately.
In PF independent “cities” are basically camps of people.
It makes a certain sense because every planet is supposedly post apocalyptic so having a thriving metropolis would be odd.
Another huge change is how the NPC factions have been given a great deal more power and agency. In AoW3 you could ignore a Giants’ dwelling to no ill effect. Here, if you ignore the Autonoms, or worse, help their enemies, they will come for you, and they are powerful.