Don't. It is not worth it. Unfortunately, Radeon doesn't wanna support mGPU properly. They always wanna put all the work on devs and they refuse to give devs any support or tools to optimize for mGPU. ImGPU works well in very select games, but stutters very badly in most if it works, is super buggy, or doesn't work at all. Just stick with the single card, upgrade to Radeon VII or wait to see what the Radeon and Nvidia cards are gonna offer. If you wait, all the current cards are gonna drop in price AND you will have access to the newer GPUs. Win-Win