X99 Build for 3D Modelling and Rendering

I doubt ECC will make a difference in 3d. More is better applies here, with the exception of latencies. For efficiency, you want the highest frequency possible with decent or tighter timings, something like 1600 8-8-8-24 @ 1.5v (can't explain why but low voltage is a thing for stability).

Looks like you are talking about DDR3. Timings and frequency are a lot higher on DDR4, which is what the OP is going for.

Also with DDR4, at the moment you wont notice much difference between the bottom and top end other than the price.

might I suggest http://uk.pcpartpicker.com/part/asus-motherboard-sabertoothx99
instead of the mobo you chose