Clean and energy efficient LED dimming

To much detail?
Hm, but nobody wants flickering lights in the living room?

Also the cables to my sleeping room ans bathroom will be around 10-20 meters.
In the moment everything is open - but when the wallpaper is done it's to late to change
something. So i need to make sure everything is planed correct and thats the reason
i read allot.

So what will be the best solution for my 12 Volt house lightning where everything can be dimmed?