How to smartly wire door/window contacts/buttons/LEDs? HA vs Dali-2 vs KNX etc.

Again, just forget it. You are late and building with the wrong company.

What you are writing is pure DIY smart home without any concept, but with a massive amount of sources of errors and incompatibilities due to the numerous different systems you mentioned. It may sound a bit harsh, but my second sentence simply applies here. You are mixing up a thousand things and haven’t even remotely understood the KNX topology. Everything you are doing now is off target or will definitely not lead to it.

Sometimes it just isn’t meant to be, simply and plainly because "Du bist du spät und baust mit der falschen Firma". You still have the option to go with a big box full of Shelly UP actuators – IF you at least remembered to use switch boxes with sufficient depth.

Think of Access Points. I will also work with Shellys and 60 boxes, so don’t worry about that. What you imagine and what you actually implement in the end are two different things. You can plan a lot, but if the circumstances don’t cooperate, it often just doesn’t work.

Thank you all for your answers! It helped me in my decision-making! Yes, I decided against KNX / Dali, there is still way too much unclear about what should go where, I still have no idea where I want which LEDs, and I also don’t know yet how I will use the rooms where something is placed. I have now installed door/window contact cables to all doors/windows either directly or partly through empty conduits (where CAT7 is planned to be laid anyway). I will then read them via Konnect through HomeAssistant (which is planned anyway), then in most rooms, living room and kitchen, I will install a second ceiling anyway, where I can then comfortably reposition all LED strips and spots as I want, calmly in about half a year when everything is set. I will then control them all via Zigbee. Roller shutter actuators either via Shelly or alternatives. Then everything fits for me so far.