Which smart home system to choose - special requests present....

Hello,
unfortunately, I’m only now, towards the end of renovating my old building, realizing that smart home is a bit more than just radiator thermostats and window contacts....
The more I dealt with the topic, the more I noticed what I have or want, and now I have absolutely no idea what makes sense and how everything can be combined. So, which wireless standard, since the chance for cables is now gone.

What do I want to control remotely and make smart?
- of course the radiator thermostats, they should automatically turn down when I open a window. Or when my boyfriend tilts one (and he likes to do that. grr). And I want to report via app whether I’m coming home or not so that it’s not heated unnecessarily.
- window contacts / handles: I want to see in the app whether the windows are closed, tilted, or really open. Maybe even a warning light next to the door when I want to leave and something is still really open.
- in the hallway, I want lights that automatically turn on when I walk through. Of course not when there is enough daylight. And at night not floodlight strength but comfortable.
- a few switches are in a stupid place and pulling cables from there with this wall... well, just forget it. A few smart thingies in the old boxes and stick a switch somewhere else – every system should be able to do that, right?
- smoke detectors: since my new drywall walls have become quite soundproof, they need to network and beep in other rooms too. It would be nice to be able to turn them off via app and check who beeped first. (Have you ever jumped groggy out of bed because of an obvious false alarm, had to get the ladder and take that stupid thing down from 3 meters high to turn it off? I hate it...)
- roof windows from Velux – so IO Homecontrol: apart from Somfy, it’s apparently not standardly controllable anywhere. Velux apparently has such a device (a hub? bridge? whatever), can I integrate that somewhere? At least automatically draw the shading when it gets blistering hot inside in summer? I would find a network great that simply opens my roof windows briefly with extremely bad air instead of just blinking like Bosch’s Twinguard does. And of course the shading, possibly opening and closing windows depending on temperature – so it doesn’t get as hot as in a greenhouse during the day and a bit too chilly in my attic room in the evening.
- outdoor irrigation: I would like to connect irrigation so my flower pots manage on their own on weekends/holidays. Water connection is there, power can be laid if necessary. Whether to use an irrigation computer, something from Gardena, a Pi... no idea yet. Currently, I’m thinking about setting up a hydroponic system, where a Raspberry Pi to remotely check water values would probably make the most sense. Or what do you think?
- music: Since a few of my stereo systems have now broken down, I’m wondering what else will come here besides the one tower with CD player and the annoying clock radio with music. A few years, well decades ago, I might have played my CD collection on a NAS to play it in different rooms. Probably no longer really state of the art.... maybe, just maybe, it would make sense to just put a Bluetooth speaker in the bathroom and hobby room that can be controlled from somewhere. I really don’t like Alexa/Siri/whatever listening boxes in the house, but maybe I’d make an exception in the bathroom. How else do you control something like this if not via phone? Put an extra tablet down to choose music?

Questions upon questions....
and to make it not too easy (otherwise you’d just say Zigbee):
I’m actually leaning towards Bosch – not only because I prefer eco-friendly rechargeable batteries over disposable minis, but also because I want to store my stuff locally on a device and not somewhere in the cloud.
That’s going to be difficult to integrate with a Pi, I suppose, right?
So whoever can shed a little light for me – I’m grateful for any info :)

I am not familiar with isolated solutions. There are enough opinions about that here in the forum. But as far as heating system control is concerned, it only works if you have classic radiators.

Realizing the whole thing definitely costs a good amount of money and a lot of time. It definitely won't be easy. Either you bring 25 systems into the house for all the scenarios. That would actually be the easiest solution because the user interfaces are usually very user-friendly. However, comfort drops to almost zero if you have to install so many apps.

I think you can achieve quite a bit with Shellys and iobroker. But there will have to be some tricky solutions, for example for the Velux situation. Unfortunately, I'm no longer really up to date on the subject, but they also have a strong forum... I would definitely ask there again, because they can tell you directly what is possible and what is not.

Something is already said about the thermostats above. If you have a new underfloor heating system, then you can cross that off.

Do the lights in the hallway refer to ceiling lights? Or are those wall lights or spots at ankle height?

I can't answer about smoke detectors and switches. Irrigation should be possible.

A new system will almost certainly be needed for the music. Sonos for example.

The whole thing can then be controlled with the phone, and if you want, you hang a tablet somewhere centrally to have an overview. For example next to the front door to check the windows.

Very, very unfortunate that you didn't deal with the topic earlier. KNX would be the best solution and, in my opinion, also much easier to install everything.

well, a complete renovation was never planned, so it would not have been possible to rewire everything anyway. That's why I think KNX wouldn't have been a real option.

Radiators: normal, no underfloor heating.
Lights: wall lights.

I haven't really dealt with the shellys yet, maybe I should catch up on that...

Since a "system" will not come about with you anyway, for various reasons, you need a higher-level instance that covers the greatest possible functionality and brings the island systems more or less under one roof.

In other words, you need, for example, Homeassistant or IP-Symcon or Savant or Nodered or or or...

Once you have chosen a favorite here, you can look for the "systems" that then can be integrated as easily and stably as possible.

It may then be that you use EnOcean window handles, Nest smoke detectors, Hue lamps, Hunter irrigation, and thermostats from Tado.

So you have to put the cart before the horse. Not buy a bunch of electronics first and then try to make everything work together. Instead, first choose and set up the platform and then buy components that are suitable.

That could be done entirely with Control4 and, for example, OPUS GreenNet. However, you don't do Control4 yourself, and it won't be cheap either, but it is maximally flexible regarding "third-party devices." Integrating everything into one system either costs a lot of time or money. You can choose. In general, what Mycraft says applies: first find and establish the top control level, then select the rest based on compatibility.