hi
I have good news for thoes who ask if it is possible to mine with rx and gtx at the same time in a rig. The answer is yes and it is really easy to do so. Just install the rx driver first and let the system restart then easily install the gtx driver and another restart means all the gpus are listed in device manager and your system is ready to mine.
In case you dont know anything about the suitable driver for modded bios dont hesitate just ask me.