Yeah. Both are powered properly..anyway it work right now..i change the slot as u say.. 5700 to bottom and 1070 on top..and it work fine..Might have to do with two gpu's of different Makers. This motherboard doesn't allow sli so the bottom slot so likely doesn't use the 1070 in there.
You tried with the RX 5700 in bottom slot and 1070 in the top slot?
Both gpu have appropriate power connectors?
Why even mix?
Ahaha..yeah..1070 for games..5700 24/7 on mining..since the $$ more than 1070..Could only think of mining as the answer so get rich.😁
Glad the way i said works, but for games it likely will use the 1070 then, keep that i mind.