Purchase decision small semi-detached house 100 sqm from 1930

It is completely irrelevant. Ventilation is the magic word. Only very good windows without insulation are somehow inappropriate. Then you have good, tight windows and a facade that doesn’t retain heat. But I assume the facade insulation will still come? Modern double-glazed windows are already quite tight and make ventilation indispensable. I don’t understand this logic of the window manufacturers. For us, it was the other way around; the insulation was already there, but older double-glazed wooden windows were installed. With the new triple-glazed windows, heat is retained much better in winter and cold in summer. Of course, you have to ventilate all the better then, but you should do that with modern double-glazed ones too. But you do that anyway. For me, ventilation is simply important for well-being and not a necessary evil.

No, there will be no more facade insulation.
Only a blown-in insulation of about 6cm might be possible, that could still follow.
But there will be no ETICS. It simply exceeds our budget, to be honest.
I had thought that with new windows, a well-insulated roof, and well-insulated dormers, I could already achieve a good effect.
I guess it will simply come down to good old classic ventilation.
So understand that I can definitely have triple-glazed windows installed.
I will then inquire about the prices and calculate everything. However, the statement from the appraiser and the window manufacturers still makes me suspicious...

The problem with "too good" windows is that the moisture no longer condenses on the windows, where it is still relatively easy to see and quickly wipe away or ventilate, but rather on the exterior walls, preferably behind cupboards (little air exchange), etc., where it goes unnoticed for longer. Uninsulated walls can also become very cold in winter, even if the room is still relatively warm overall. That means the dew point is quickly reached there. The consequence is persistent dampness, ideally on wallpaper, and the result is mold. So even if you ventilate, moisture damage can occur at critical spots. As mentioned, behind cupboards this is difficult. Whether double glazing really makes such a difference compared to triple glazing, I dare to doubt. Compared to a completely uninsulated wall, double glazing will insulate better than a completely uninsulated brick wall anyway. So creating a ventilation concept would be good, insulating the walls even better. In doubt, simply place thermometers and hygrometers with apps at all critical spots. Download the dew point curve from the internet and whenever the dew point is undercut, turn on a heater and open the windows wide (unless it is raining).

If you don't insulate the facade, I might not install new windows at all. I would suspect that the investment wouldn't be worth it then. And the problems described here might actually occur because you can't keep up with the ventilation. Personally, I would say all or nothing. Either insulation and new windows or leave it as it is.

So replacing the windows is unavoidable. The ones currently installed are junk, I can say that for sure.
The new roof for €40,000 probably will never pay off, but for us it's also about making the whole thing look a bit nicer and bringing it up to date and getting the place reasonably watertight. We are also enlarging the window areas in some places to make everything a bit brighter and friendlier. It's not always just about "Is the investment worth it?", other factors also come into play.

The real question is just whether double or triple glazing - here even opinions differ or basically it probably doesn't matter much. For me, in the end, it's just a math exercise.

As a layman, I just can't imagine that the heat currently lost through the old windows, and that will be a lot, then escapes to the same extent through the walls. And somehow I also don't believe that everyone who just replaces their windows and doesn't renovate the entire exterior shell for €100k has to deal with massive moisture damage. I don't want to question your knowledge with that :-) Don't get me wrong.

Behind the dormers, there is 30cm of masonry.

I find that hard to believe or to verify from the drawings.