More efficient way of cooling and heating a 1700 sw. Ft. Home

[Rafael Zavala]

I bought a 1700 sq. Ft home thatt was built in 1915, was a foreclosed two years ago, so its been vacant. Heating system  needs to be replaced, it used water radiators  with an oil furnace. House does not have duct work, has 10 ft ceilings. Im looking  for the best way of cooling and heating the house, since i will be flipping it. I have a couple ideas, firts one it to continue using the radiators, update the oil boiler to a gas combination boiler for heating and hot water use. And then to use a split system to cool the house. Second idea, would be to use a heat pump to cool and heat the house and use a gas water heater for hot water supply. And just  get rid of the old radiator system. But i heard heat pumps are not very efficient  in very  low  cold temperatures.  Do split heat pumps have supplemental electric heat as a regular heat pump. What would  be the best route? Any other ideas, thanks!