How to avoid melting a 3D Printed Chandelier with LEDS and DC Voltage Drop Across 7m Cable Run of 100A 12v DC
The main power loss is in the LEDs, they are at best 30 % efficient, so 70 % of the 1 kW will end up as heat in the chandelier. 

At that wattage I suspect a good PSU to be 90%+ efficient which would be only around 100 W as heat compared to 700 W by the LEDs which are directly mounted on the chandelier.

So I'd say your gut feeling is wrong (the PSU being the main heat generators).

I'm not sure for what you want to use this, but 1 kW LEDs will produce around 100.000 lumens (100 lm/W assumed). That is roughly the equivalent of a 5000 W halogen bulb. This is very bright...

Calculating or guessing the temperature this contraption reaches is quite difficult and for my limited time right now not feasible. Sorry for that, maybe someone else can answer that part.