Laptop with NVidia and Intel GPUs, choose the graphic board connected to a USB-C adapter

I am using a laptop that has both an Intel and NVidia GPU, with a second monitor plugged on an USB-C adapter and bumblebee enabled. By default, the USB-C adapter connects to the NVidia board, then I am able to use it with bumblebee + intel-virtual-output. Now I noticed that sometimes, randomly, the USB-C adapter connects to the Intel board instead, which I prefer (because it is more direct and display is more fluid than using intel-virtual-output that copies the framebuffer in the background). Since it sometimes happens, it means that it is at least possible. Is there a way of controlling that, that is specifying which graphic board the USB-C adapter talks to ? Note: if I deactivate the discrete GPU in the BIOS, then the USB-C connects to the integrated Intel board. If the discrete GPU is active, then 9 times of out 10 it is connected to the USB-C, and 1 time out of 10 it is the Intel GPU.