Annuity loan vs. annuity loan + large housing loan

55K€ gross is at least 2600€ net and times 2 that is 5200. So 1150€ is not much. For parental leave there is parental allowance and even if only a 20-hour job is planned afterwards, you (if married) would still have 4255€ + child benefit available. Many home builders with two full earners have less.

what speaks against my conservative approach? if anything remains, it will be specially repaid children, vacation, 2 cars... that all costs too.

I also approached this conservatively with a 2% repayment rate and an installment of around €850, since my wife was pregnant at the time of the loan agreement 2.5 years ago and it was not clear how many hours she would work after parental leave. We currently have around €3600 net together (already subtracting 1 company car), a second car is also available, a bigger and a smaller vacation are possible every year, and we also have a child. Nevertheless, we want to make more special repayments than you and have already managed to do so twice. We are quite frugal with going out or similar activities, so one can certainly spend more on life, and our daycare fees are also reasonable compared to other regions. However, when I calculated future earnings for you, I only included a 20-hour job. Whether you plan more or less is something you have to decide for yourselves.

About the financing itself
1.) What about kfw?
2.) If you plan no or hardly any special repayments, variant 2 probably makes more sense (provided the allocations and changes in the rate work out).
The more you repay early, the shorter the term, and the sooner variant 1 or even a shorter term with a better interest rate becomes worthwhile. Therefore, you really have to look at what special repayments are feasible.
Then there are also the disadvantages of variant 2 in old age. (please inform yourself carefully about what happens if you want to move out of your house for whatever reason) Additionally, you actually wanted a transparent financing, which would also speak in favor of variant 1.

A small note:
I actually don’t like building savings contracts (Bausparfinanzierungen), but I admit that variant 2 does not seem unattractive under the conditions you set.
You just have to be aware of what you are signing.

I also find a rate of 1150 to be a lot of money. In addition, there are about €300 for ongoing maintenance costs/insurance for the house. Therefore, we will not change anything about the rate.

KfW is not an option because it is not a KfW 70 house. We have not factored in program 124. The interest advantage is marginal. And the remaining debt of almost €40,000 would have to be secured again through a building savings contract.

Rate adjustment in variant 2 fits.

Special repayments also have an effect in variant 2.

The fundamental advantage of variant 2 is precisely the hardly existing remaining debt after 25 years (€10,000), whereas variant 1 still has over €70,000.

Disadvantages of Wohnriester are partly known. Is the calculation from the financial advisor correct?
€50,000 contract * 2% = €1,000 times 20 years = €20,000. This would then have to be taxed at the personal tax rate upon retirement age. In plain terms, about €5,000 per contract. An acquaintance explained it differently to me. There would be about €20,000 "tax debt" remaining that one would have to pay off until the age of 87. If you die, the tax debt passes on to the heirs.

Basically, I don't like building savings contracts either. But the mentioned advantage speaks more for variant 2.

However, I do think that at the end of the day both offers are not too different.

I am happy about the current conditions though. I have received about 10 offers from various providers/banks. No one comes close in terms of the interest rate.

My involvement with Wohnriester was already 2-3 years ago, so I can no longer say anything about the taxation afterwards.

At that time, I excluded Wohnriester for us not for tax reasons, but because I considered the risk too high that if, for whatever reasons, one has to/wants to leave the house, then the repayment of the subsidy could be an additional burden. Whether because one wants to sell due to professional reasons and relocation, because one physically can no longer maintain the house, because it is no longer financially feasible, etc. There are occasional ways to avoid repaying the subsidy, but whether they fit is questionable.

Better to complete the Riester plan independently of the construction and take advantage of the subsidy.

There are enough options not to have to repay the subsidy even in the event of separation. The repayment options for the building loan are much more flexible than for annuities, and this is during the phase when one (hopefully) has more money available than right after construction. It is a mystery to me why [Wohnriester mit Bausparvertrag] is almost always spoken of negatively here.