I have not been using public charging stations since the Kia supplied Level 1 charger will fully charge the PHEV overnight. Electric range is 26 miles, more than enough for my daily usage.
To the best of my knowledge, there are Tesla style charging stations, and then there are all the other Level 2 units which conform to the same US industry standard. There may be differences in available charging rates, but the charging interface standard provides for automatic adaptation to the different rates. PHEVs do not use or need the high speed DC Level 3 chargers since their batteries are smaller than EV only vehicles.
In the Niro, cabin heat always comes from the gasoline engine. No electric heat other than the heated seats and steering wheel if you have those options. I find the seat heater faster than cabin heat and more useful on my short commute.
The A/C cooling compressor is electrically driven, so running in HEV mode simply helps keep the battery topped off. Again, for my short commute topping off the battery is not needed and I intend to run in EV mode most of the time.