The main thing about the FFE is that pre-2017, they didn't have any form of DC Fast Charging option. Plus the resistance heater (similar to LEAF S trim, but unlike LEAF SV/SL which has a heat pump) uses a lot of power and the smaller battery... it can be dicey if you drive a lot in cold weather.
FFE 2017 has 50% larger battery, SAE Combo fast charging, but otherwise it's the same.
Other thing to keep in mind is that the stock 12V battery tends to go bad by year 3, so expect a 12V battery replacement in the near future. The car won't "start" or will act finnicky and you may not be able to open the trunk (so don't keep your emergency jumpstart kit in the trunk).
I believe the Ford warranty for the "hybrid/electric drivetrain" components is 8yr/100K miles, but Ford doesn't have specific battery degradation guidance like Nissan does. On the other hand, the Fords have active Thermal Management, which the Leaf doesn't, so in theory (assuming the previous owner and owners in between kept the charger plugged in during any extreme hot or cold weather) the battery's degradation is less of an issue. In theory.
2017 Ford Focus Electric (Magnetic)
2017 Ford C-Max Energi SE (Kona Blue)