House construction, please provide decision aids for the details

Good morning, actually we wanted to be living in our own home by now, but unfortunately or luckily it didn't work out. So now freshly "separated" from our former developer (Hv.), we have handed the project over to an architect. But even here you have to make decisions regarding building services etc.
That's why I'm asking for help here :)

No idea if I should ask the questions better in the subforums or something, if yes sorry. Just let me know and I'll do that.

General information about the house:

1. Single-family house with 2 full floors without a basement

2. Solid construction with T10 or T8 without thermal insulation composite system. Which brick is still to be decided when the offers are in, it's mainly a cost question)

3. Gas condensing boiler with solar thermal for 50% domestic hot water on the roof

4. Automatic ventilation system with heat recovery

5. approx. 170 sqm living space with approx. 800 cubic meters of enclosed space

6. Open roof construction i.e. no attic

Now to my questions:

1. Because of the roof pitch "normal" roof tiles are not possible. The architect has now given us as options roof panels, I believe that is fiber cement from Eternit or aluminum roof shingles from Prefa. I would like to know your opinion on this. Both regarding durability, watertightness but also noise (since the bedroom ceiling is practically the roof).. Especially with rain I imagine this to be difficult and very loud, or am I wrong?

2. Which gas condensing boiler in combination with a solar panel share would you recommend... as manufacturer etc..

3. Controlled residential ventilation - what experiences have you had here? Which manufacturers could you recommend? I am especially interested in the possibility of cleaning in case the much-discussed mold or germ issue occurs. As well as maintenance costs.

Many thanks in advance

Regarding 1.) there will still be insulation in between, about 25 - 35 cm. So the ceiling of the room is by no means directly the underside of the roof. What is the roof pitch?

Yes, I understand that between the actual roof and the ceiling there is still insulation, drywall, etc.

Nevertheless, I am asking about the noise level, for example from rain.

The roof pitch is a bit complicated. It is a gable roof with a crosswise roof ridge. I can't say for sure, I would have to ask the architect again. In any case, it should be like that, so grateful roof tiles like [harzerpfanne] or something similar wouldn't work.

Subsequently with the heating currently being annoyed, a flow temperature of 3 degrees is assumed; should this be reduced?

Still, I'm asking because of the volume, for example during rain.

Well, personally I think this argument is overrated. The rain only really bothers you during the 30 minutes of the falling asleep phase. And then it has to be really pouring heavy rain to be disturbing. Now you can figure out on how many days it actually rains heavily during those 30 minutes. As someone who has slept for years "under a skylight," I can say that this was rarely the case. Therefore, in my opinion, other arguments should be more important.

But to each their own...

Well, personally I find this argument overrated. The rain really only bothers during the 30 minutes of the falling asleep phase. And then it has to be proper pouring heavy rain to be disturbing. Now you can calculate how many days it rains very heavily in those mentioned 30 minutes. As a longtime "under-the-roof-window sleeper," I can say that this was rarely the case. Therefore, in my opinion, other arguments should be more important.

But to each their own...

I can follow your reasoning there. Only so far it's just a speculation, which is why I am asking "if" there are differences or recommendations. Because there are indeed uncertainties. For example, how does an aluminum roof react in summer to sunlight? I mean, metal expands much more than concrete, cement, or clay.
Taking the roof window as your comparison, it usually only has a very small surface area. What if the whole room is like having a huge roof window because of a metal/aluminum roof...
As I said, just asking if you have aspects on your side that are negligible, or that speak for one or the other... and/or experience values or recommendations.

It's like my question about heating. In the internet "maze" there is a lot of information—some say the flow temperature should be as low as possible, around 28-30 degrees, others say 35 degrees, others again 40.
Because the additional costs caused by closer piping loops (with lower flow temperatures) are not offset.

I'm a complete newbie here and asking the nerds ^^ ;-)