ciao @SQA i am not in OSX because my new GPU is not supported by now so for me it is more complex to help you.
Try to understand the same my advices 😛
Regarding internal audio (chip o motherboard Realtek USB 2.0 audio---> it is called so)
take a look to these pictures:
if you connect your case audio cable here..you can use audio without any problems!
if instead you have a speaker connected on green backplate jack, audio is not detected.
to have it detected you have to off your pc, then disconnect speaker jack from green backplate place then, on your pc and whe it is in OSX attach again speaker jack to backplate...
regarding BT and WIFI..you have to ask to some users using it like @Arrakis, @Ploddles or @Driftwood
then regarding MMIO part of your hope to have a perfect system: 🙂
read and try to understand here (thanks @iGPUwho writes this detailed article after we have discovered the "immense" potential of MMIO areas for our systems :
TRX40 Bare Metal - Vanilla Patches (Yes it works...but..Proxmox is better?) - Page 33 - General - MacOS86
About your dual monitor detection:
Check if you use weg or not (Whatevergreen.kext)
try to enable or disable it
if you have the same problem you have to try different GPU port
On my radeon XFX in the past one DP port was not detected in any condition from OSX...but..i have ha Mojave in those time 🙂
be happy..now your system starts..you have to refine better with a little effort to do yet