They should. I have currently AMD + NVIDIA GPU in my PC, the lanes are split on the motherboard (it can be 1 x16 or 2 x8). There is a bit of fiddling with driv

They should. I have currently AMD + NVIDIA GPU in my PC, the lanes are split on the motherboard (it can be 1 x16 or 2 x8). There is a bit of fiddling with drivers but it is possible to have one manufacturer working in compute only mode and other as graphics and compute.