Long time log fire user, now have moved, and have two heat pumps.

I assume that the higher the temp differential the higher cost, i.e. 10 outside, heat pump set to 20 is cheaper than 4 outside, heat pump set to 24. Obvious I guess.

Downstairs there are two living rooms, and kitchen, the living room where the TV is takes a bit longer to warm up.

So, is it better to heat at say 22 on low fan, or say 18 on high fan. To, 1) reduce costs, and 2) to promote more air movement?

I am a heatpump noob.

Edit: Fujitsu Inverter, Cooling 7.4kW heating 8.5kW