That is right. It seems that the RX 480 is only good at Ethereum mining. But it is less efficient than 1070.
If you just want to mine the Ethereum, the 480X is the best. But if you want to mine other coins, 1070 is the best.
That is right. But the 1070 is too expensive. We may have have ROI. Maybe we can wait for the 490X.