700F has always been the standard fixed tip temp for general purpose through hole soldering.
600F for finer smaller SMD and sensitive stuff.
800F for beefy stuff.
These are your standard old school Weller or metcal tip temps.
But of course these "standard" temps are entirely dependent upon the thermal capacity and recovery time of your top and element system. And you can't just go by the wattage.
So anyone who claims one temp is best without measured performance data on the tip and system being used is talking out their bum.
Yes, old school F here.
IMO 250C is too low for all but the best capacity irons like JBC or Metcal et.al.
For SMD I'd think 550F, 600F, 650F is likely to be the sweet spot.