I have a i5 6500 and RX 480, in High Sierra I now have full hdmi and DisplayPort audio working set up is easy, I don't inject ATI or fake IDs only ( inject Intel, ig 0x19120000 ) fixes for IGPU graphics. Sleep works, audio, full accceleration, etc... no fixes needed except name R9 xxx, but if you do inject ATI it will change the name for you automatically.
For my Haswell pentium G3258 I use inject Intel, fake ID 0x04128086, ig 0x0D220003 and it works as well with RX 460 with audio, acceleration, etc....
Polaris cards are working great in High Sierra beta, we've had audio before with fixes but it was very slow and garbled, now it works and one user has 8.1 sound through DisplayPort working.