I would expect a lot more miles out of a tank from a Plug-in...
No electric heater, just engine fluid to the heater core, Niro turns on the engine on just to warm the cabin.
I have driven from stop to 45 3 or 4 times on EV, and dozens to 40, countless to 30. I have caught it in EV at 60 mph, flat level driving dozens of times, usually lasts about 1 1/2 miles.
I have gotten several 620~644 mile tanks on my '17 Niro LX. Those tanks were probably 85%+ city stop and go driving, 40 mph and under.
Welcome to Niro!
The 1.6 Kappa engine is GDI. It is not at all like a Toyota with MPFI.