I SOLVED IT!!!
OK so afer long 4h of sleep..... I've been another 3h with this and I finally fixed it. I have full hardware acceleration and h264 times are faster than my old iMac.
@pastrychef Your EFI "as is" doesn't fully work for me. I mean,
everything works as of now, except Quicksync / h264 Hardware acceleration.
@corint1 My BruceX test gives a result of 12s average, around 70% faster than my old iMac. But my h264 export times were like 5x or even 10x longer than the same old iMac (no sense at all).
As I said I've been trying a lot of stuff, and I finally got it, only changes needed:
1. Enable IntelInject in Clover.
2. Add connectorless address 0x59120003 to ig-platform-id.
Now everything is fine!! My export times in h264 are around a 30% faster than the old iMac. I guess the lower gain compared to ProRes is due to the CPU being clocked at 3.7GHz while my old iMac's is at 4,0GHz I think? Or maybe I don't get 100% hardware acceleration due to kernel patchs and everything not being as optimized as an actual Mac system... I don't know, but still, very happy with the results as of now
Also, curious detail:
Transcode to Proxy media of a 5min 4K clip is a 20% slower with the Hackintosh.
Transcode to Optimized media of the same clip is a 35% faster on the Hackintosh.
Again, I guess that in order to downscale to proxy it uses more quicksync and in order to convert to ProRes422 it uses more actual CPU power? I don't know.