Is heating load calculation with desired temperatures necessary?

Thank you very much for all the information!

Our idea is also to eventually be able to operate the underfloor heating with a heat pump. At least we want to remain flexible there. And with heat pumps, the heat load calculation is even more important. How would you proceed in this case? Should the heating installer create a heat load calculation for a heat pump and accordingly determine the loop spacing of the heating pipes, or is that too much since a gas heating system will be installed? I could imagine that he might think I'm crazy. Or should I just tell him that the loop spacing should be a flat 15cm? What do you think?

Why should the heating engineer show you the bird? Just tell him what you want.

Since he will install a gas heating system but has to create a heating load calculation for a heat pump that may come in many years. That seems strange to me.

Well, if you name the reasons, it's not so strange after all? Everyone is different. It's not wrong to take a closer look at the whole thing. You wouldn't be lying if you said you are considering getting such a system instead of gas.

You simply specify at which flow temperature and return temperature you want to achieve which room temperature.

For example 30/26/21. And that at your design temperature. From this, the pipe spacing is then determined.

If you also specify the maximum heating circuit length with max 100m and there are no circuits that are too short (min. 80m), it should run optimally for a later heat pump.

You simply specify at which supply temperature and return temperature you want to achieve which room temperature.

For example 30/26/21. And that at your design temperature. This then results in the pipe spacing.

Unfortunately, my knowledge is lacking here. I have no idea which supply temperature and return temperature I should specify...

Based on my current knowledge (which, as you can see, is very limited) I can only specify the desired temperature per room, that is:
Bathrooms 23 degrees
Parents 22 degrees
Living/Dining/Kitchen 22 degrees
Child 22 degrees
Office/Guest 22 degrees

These are our temperatures (which certainly deviate from the standard) at which we feel comfortable and currently have in our apartment.

Could you perhaps help me out with how I now relate these to the supply and return temperature?