What about the power consumption when mining ethereum? Any info?
Not sure what you mean by this , the power consumption depends on the card not on the Algo you are mining. X11 gives you a higer Hash rate than scrypt on the ALgo basis but youre
still pushing the card to its limits so power consumption does not change.
a 280x pulls around 240 at the wall
this is incorrect, the power consumption depends on the Algo, the same card can pull for example 270w on scrypt or less than 200w with other algos. you can find a lot of tests on bitcointalk, like this one: https://bitcointalk.org/index.php?topic=694431.msg7916782#msg7916782
Thats because the Algos are not fully optimized for the cards, it depends on how hard you are taxing the cards, if an algo only taxes the GPU's by 30% it will or course use less power but all that means is you are not using the full potential of the card.
An algo can use only the 30% of the gpu power because of the memory bottleneck, in this case you can do nothing and you are using the full potential of the card
That is right. Also for SHA256, it uses little memory bandwidth so you can reduce the memory speed.