Which heating system and how to combine it with photovoltaic / solar thermal?

Without. They are still too expensive to be worthwhile. Can be retrofitted later if it makes financial sense. Currently, however, it is too expensive.

Without. They are still too expensive to be worthwhile. You can upgrade later if it makes financial sense. But currently it is too expensive.

Okay! Maybe a subsidy program will be introduced for that in the near future...

Gas must be phased out to zero within the next 15 years. I wouldn’t start with it now. Regarding Wolf: As far as I know, the manufacturer has currently put its 4 kW model on hold. That means there are currently only the 7 and 10 kW variants. They are very good, but clearly oversized for a new building. Make sure you get any current model with a heating capacity suitable for the house.

I haven't searched through the OP's history, but I haven't read anything about heat load calculation, region, or size of the house in this thread. Therefore, I wouldn't say that 7kW is too large. Especially since I believe we are talking about a modulating variant.

120 sqm without a basement on the Mosel is something different than 160 sqm plus heated basement in the Allgäu.

A new building that requires 7 kW heating capacity is, in my eyes, a newly built old building. And in the eyes of our legislators, in my opinion, no longer permissible. Therefore, I would bet that the heating load is somewhere between 3 and 5 kW. Without knowing more about the house.

That the CHA 7 can certainly be used in such a house and that it probably delivers quite decent results is of course also true. It just costs more.

A new building that requires 7 kW heating power is in my eyes a newly built old building. And in the eyes of our legislators, in my opinion, no longer permissible. Therefore, I would bet that the heating load is somewhere between 3 and 5 kW. Without knowing more about the house.

However, it is also true that the CHA 7 can certainly be used in such a house and that it probably delivers quite decent results. It just costs more.

So I don’t really know either. You somehow leave the framework conditions out. If you follow the magenta-colored forum, there are plenty of single-family homes that are KFW 55 and due to volume and location end up with a heating load somewhere between 5-7 kW (according to Trenchplanner). That has nothing to do with old buildings or anything else. The OP is aiming at KFW55 or maybe even worse. This is not the topic here but especially now that nothing is being subsidized anymore, it often doesn’t make economic sense to struggle additionally. First, I would think about proper planning. That means, if in doubt, paying a few hundred euros and hiring a TGA planner. See what comes out of it and then decide accordingly.