It’s just an air conditioner with an extra valve to reverse the flow.
They work in much colder weather than you are imagining.
They are more efficient than you are imagining.
They are even better if you look for the latest models coming out of the far east.
Actually do the calculations for how much power you need - don’t just let the installers say “This house currently has x kW of heating, therefore it will need an x kW heat pump” (same for the air conditioning mode)
It’s probably better to have a resistive heat backup for occasional extreme-cold days than to have an oversized heat pump.