My results may arrive later than you expect. I originally had two W5700X MPX modules, and I recently replaced one of them with a 6900XT. when I use both GPUs for export in DaVinci, both GPUs are around 30% occupied. When I formulated to use the 6900XT single GPU, it reached about 50%. The single 6900XT exported a little faster than the dual GPU. My guess is that the W5700X module is limiting the 6900XT. The results might be better with dual 6900XT.