I got a CPO that was originally a company car used by a Ford executive - it was barely a year old with 7800 miles on it.
Car has been mechanically and electrically reliable over the last 10,000 miles. Never needed any warranty repairs so far.
My previous car was a 2013 Fusion Hybrid SE - essentially the same car minus the plug in capability - and it was mechanically reliable as well though it had a few minor non-drivetrain-related issues fixed under warranty (peeling sunglasses holder, improperly calibrated left turn signal, cracking sound when braking that required new washers. It was also the very first production run (July 2012) and any flaws it had were "patched" in later model years.
If the 2016 you're considering isn't CPO, get a PPI before doing anything - check for rust, error codes, peeling trim, etc. Test all the on-board tech like blind spot monitors.
Titanium and Platinum are the preferred trims, especially if you live in a hot area since they're the only way to get cooled seats. While you can get the rest of the cool tech like blind spot monitoring and adaptive cruise on the SE trim, most SE buyers opted for basic models and so you're unlikely to find a used SE with all the tech.