Hello @toadbroth 
If you need the nvidia driver, then you will have to install 390xx for a Quadro P2000.
Nouveau is a alternative free open source driver for nvidia cards, but it is far from being perfect and stable for all GPUs.
I would say: If the nouveau drivers, which runs your Linux by default, isn’t stable enough, then you have to use the 390xx driver of nvidia.
This should auto-detect der GPU and install the supported driver:
mhwd --auto pci nonfree 0300
or this will force to use a specific driver:
mhwd -i pci video-nvidia-390xx
https://wiki.manjaro.org/index.php/Manjaro_Hardware_Detection_Overview
https://wiki.manjaro.org/index.php/Configure_Graphics_Cards