I think Y-tiling is turned on via the driver's Info.plist, so GfxYTile is probably not needed. That's probably why it is not needed anymore on 10.12.5. But, since it is already turned on by default, it probably does nothing if injected. And... I think Clover may be automatically injecting it for config.plist/Graphics/Inject/Intel=true anyway.
Clover will inject a fake device-id automatically if you don't specify config.plist/Devices/FakeID/IntelGFX=0. That might change, but it would need to be conditional within Clover code (depending on version of macOS boot target), and I'm not sure if that work will actually be done.
As I wrote here:
http://www.insanelymac.com/forum/topic/324194-pre-release-macos-high-sierra/page-48#entry2447474
.. you might need -disablegfxfirmware kernel flag
(I needed it with the ASUS Z270-AR + i7-7700k setup here...)
I wrote about what a typical setup might look like:
http://www.insanelymac.com/forum/topic/324194-pre-release-macos-high-sierra/page-48#entry2447504
One thing nice about 0x59120000 for desktop use is that the LVDS connector present in 0x19120000 was left out, such that the 0306 connector is active, therefore no need for the "4 displays" patch (or connector re-arrange) that was needed with Skylake 0x19120000.
And, of course, sleep is still broken, which makes a compatible graphics card almost compulsory.
At least that's how it stands in the 10.13.dp1. I suspect 10.12.6 (and the special 10.12.5 build) is the same...