Installer will halt when trying to boot installation media in graphical mode using NVidia GeForce 1070 display adapter. You cannot choose other display resolutions / modes in UEFI mode from Grub menus. You can only do that in legacy mode so installation is not straightforward with OpenSUSE Leap 42.3 + UEFI + NVidia GeForce 1070.
One solution is to use your motherboard built-in display driver but transitioning from that to Nvidia seems to bring extra pain to the process.
This is simple and quick. Do a text mode / VESA mode installation that will result in a working system with VESA mode which can be easily updated to NVidia proprietary driver based system. Usage of Nouveau is not possible as of yet and if you manage to make it work it is terribly slow.
I did not try VESA mode installation but in theory it should work as well.
When booting with installer media press e in the Grub menu and set kernel parameters text and nomodeset. If you want to try VESA GUI install just put nomodeset. Remove all other graphic kernel parameters (splash etc).
You should now have a running GUI OpenSUSE with VESA graphics.
Next install NVidia proprietary drivers by starting YaST repository management, adding community repository for NVidia, installing recommended packages and rebooting.
The NVidia driver package in my case was of the previous kernel version so be aware and check that the NVidia packages match your kernel version and downgrade kernel if necessary.
But I did add online repositories during install which gave me latest package versions straight up so that may have caused the situation. If you install from media you will probably be safe.