1. AMD cards always handle dual mode better than NVidia. Especially 290(X)/390(X) cards, they are the best. RX480 is good too. Other cards are not so good in dual mode.
but Nvidia more profitable on LBRY (1070 get 312 mh...)
Unfortunately, there is no way to get 0% drop on ETH if you mine ETH+LBC. Why? See item #2.
Fury not drop on ETH at dcri 30
On my 1070s, I've found better profitability with Claymore's ETH + LBRY than LBRY alone (only tried open source miner), as long as I max out at -dcri 500. Actually, it's the most profitable combo I've found yet, MUCH better than ETH alone, ETH + DCR, ETH + SIA, etc.
This is not true... I already attempted this. You end up at about 15Mhs Eth and 150Mhs Lbry, compared to 250Mhs Lbry. In order for Eth to be worthwhile mining like this, either network difficulty would have to go down or hash of the miner would have to go up. The trade off isn't worthwhile. This depends a lot on the price of Lbry though as it's been fluctuating a lot (as has network difficulty).