Just thought I'd confirm that you'll have headaches with a non-blower card. I installed a zotac 1080 mini in mine and I'm still trying to work out a way to keep it from overheating. Right now ive got it laying on it's side with a sort of ram-air exhaust tunnel made of cardboard and tape hooked to an 80mm fan pulling air out the bottom vents (well, now they are left side vents...). plus a little another little fan taped directly to a small grill on the rear of the card, and that keeps it from overheating most of the time, but I still need a higher cfm input fan because that lower front fan does virtually nothing.
So yeah, get a blower card unless you really want to spend a lot of time getting creative with alternate cooling solutions -in a very small space-. (ps, if you go the cardboard and tape route, use blue painter's tape, so you don't leave sticky-goo all over your case ;D )
Anyway, I don't recall having to do anything with bios stuffs. I did change the drivers, but not because of any problems with the system recognizing the card; It's just proper to reinstall drivers when changing cards, cause... stuff.
For a bit of added info that may-or-may-not be helpful; The original riser card in my x51 didn't have the ssd-slot on it, so i got a used riser off of ebay that *did* have the ssd slot, and swapped it in. the system didn't have any problems recognising the video card using either type of riser card, but one thing that was different, was that after putting in the different riser card, an issue with my pci sensor always reading 127c went away and it started reading normal/believable temps like the other sensors.
The only other thing that comes to mind atm, is that my card requires 2 power plugs, and i can't remember if they were 2x8 or 2x6 or what, but it was more pins than what the original cable has, so I had to shove an extra adapter cable in there. The original card that was in there didn't require any power beyond what it got through the pci-e bus, but power hungry cards need a good amount of extra power to be supplied through those plugs, and I don't know what plugs your 1070 requires, but if you had to do something like I did, that basically doubles the amount of potential bad/faulty connections, so you might want to verify you don't have any loose pins/wires/connections etc in that area especially the connector that attaches to the board, because the one on mine was pretty darn loose.
Oh, and of course, if you have another computer, you might want to try sticking your 1070 into it to test the card itself. I love asus, but it's always a possiblity that a card gets out the door with a defect, and testing it in another system could help to rule that out.
anywho, good luck and I hope you get it sorted