Solar for hot water/heating or better photovoltaic for electricity?

Thank you very much for your support! This is how I will proceed.
If, in the end, solar thermal has to be installed on the roof, it will only be as large as necessary to comply with the Energy Saving Ordinance. Would such a small solar thermal system then be used to support the heating, for hot water, or for both? Are there any recommendations?

This is a matter of cost. How much do options 1 or 2 cost you? And what can you expect in terms of heating support in winter? Are any additional costs worthwhile?
It depends on the location, the planned solar thermal tilt + orientation....

Are the requirements of the Energy Saving Ordinance now so high?

An independent energy consultant should be able to provide a solution. To my knowledge, when using gas, solar thermal systems are still uneconomical in single-family homes.

A heating system is never economically profitable. Solar thermal systems are not either. Controlled residential ventilation neither. This is not the approach of the Energy Saving Ordinance - which is also not an economic instrument, but is intended to save energy.
Alternative measures to avoid Solar + Gas would be:
- Reducing transmission losses by 15 % (--> KFW 55; higher investment for better building envelope tends to be more expensive than a small solar thermal system; uneconomical like all other measures costs insulation <=> saved energy)
- if applicable, controlled residential ventilation, if at least 50 % of the heat energy demand is provided from waste heat (--> controlled residential ventilation tends to be more expensive than a small solar thermal system; equally uneconomical - but with a gain in comfort)

The most important thing is still the insulation
In 2014 I paid 258,000€ turnkey for 176 sqm Passivstandard. High-end fittings. A completely normal gas boiler with controlled residential ventilation – the savings compared to expensive heat pumps etc. were enormous (about 21,000€) and the energy demand is between 3,200 and 5,000 kWh. 2 people, showers daily. Few window surfaces on the north side. Average room temperature 22.5 degrees
Even though quite a bit of heating technology is subsidized, it does not necessarily have to be economical. 80 € electricity and on average 32€ gas per month speak for themselves, the maintenance of the gas boiler is 105€ per year
But there will continue to be people who spend 30-35,000€ on a heating system and wonder about the electricity bill.
For the savings of about 21,000€, I can heat for a very long time and I don't care about subsidy programs.