New building KFW 55/70 heating consultation

Hello dear forum,

I plan to build a new house around the middle of next year. Now the consideration arises about the type of heating, kfw, air-water heat pump, residential ventilation, etc....

Here are the data for the planned new building:

Single-family house without a basement, 142.86 m² effective living space, 1 1/2 floors, no gas connection available

We are now considering installing an air-water heat pump with residential ventilation + Kfw 55 or Kfw 70 without residential ventilation..

Is the air-air heat pump sufficient or what are the costs in the winter months?
One provider recommended an air-air heat pump from Tecalor, how are these air-air heat pumps??
Should one consider a gas tank with a small gas burner as an auxiliary heating??

What is your opinion on this aspect and what would you advise me?
I am grateful for advice and also for concrete examples.

If there is no basement and no gas connection, I would currently always tend to opt for the air-to-water heat pump. Whether a ventilation system is "necessary" probably also depends on the desired [Kfw Standard], but it is certainly comfortable.

What is your opinion on this aspect and what would you advise me to do?

I would provide controlled residential ventilation for comfort reasons, regardless of the KfW standard and independent of the heating system. I would not mix systems (heat pump with gas auxiliary heating). Either gas or heat pump. If heat pump, then air-water heat pump or ground-source heat pump (depending on budget and soil conditions).