I have a mixture of these two gpus in my case, they are working fine I have not encountered really any issues. I use blender and 3ds max and I have been told by a few people that having these mixed gpus you will not have access the the full features and abilities of the Pro or the RX because they are not the same. is this true, I dont know enough about this. I see both in the amd control panel and have access the the Pro setting. I am limiting my speed because I dont have the same cards.
Probably fsadough, AMD Forum expert on Professional GPU cards might be able to shed some light on your post.
I don't have an answer to your question. This is not a kind of configuration we usually test or validate. The best option is to test all three alternatives and find out on your own.
this seems to be an area that both sides Nvidia and AMD lack! there are people who do 3d modeling and like to play games and want to use a workstation card to do the rendering and use a newer gamer card for gaming. why is it such a strange concept that someone would have both type of cards? and to never have never tested a build of something you get hot on selling to customers for CAD or 3d work and never test it with your flag ship cards for compatibility . I have Nvidia Quadro cards but they cannot work with Nvidia gtx or rtx cards in the same computer. I will instantly jump ships to team Nvidia as soon as they support the Quadro and rtx setup. I have regretted switching to team red its be a battle of not compatible with my 3d apps not enough features or support.